First of all, I doubt you are a lost cause. I don't know about Islam, but the Christian God has his arms wide open to whoever choses to repent. The sinner on the right side of Jesus accepted him as his God during the crucifixion and Jesus has promised they'd soon meet in heaven. That is, someone who has committed lots of crimes was forgiven moment's before his death thanks to his faith.
Christian tradition is based on the acceptance of Jesus Christ as your saviour. He's the "evolved" scapegoat used by the Jewish to take the sins of humanity upon him. By believing in his godly nature, one admits his sins too have been washed. This way the believer starts building a relationship with the personal God in the person of the son sent to Earth. Heaven is, supposedly, a place of reunification with the creator, one where his love will be felt forever.
Hell is a much more controversial concept. For many reasons. I can only touch the surface of it (no pun intended). In the Old Testament, all people died and stayed dead. There was no hell. Death was the final void. The idea of hell developed much later, becoming more and more complex in the New Testament, as the place where the "beast" and those who worship him (talking about Satan here) will be sent to burn in an eternal fire when Jesus returns. Whether the fire is eternal or the suffering in it is eternal is still a matter of debate among theologians. Somehow, at some point, people became threatened by hell for their sins. Small sins? Big sins? According to some scholars (I believe Craig is among them), any sin is deserving of hell, since it is a slap on the face of an infinite being. The nature of God therefore makes any sin infinitely heavy.
But then comes Jesus, who takes all our sins upon him. By accepting him, we accept his sacrifice and this takes the sins off our shoulders. So Christians will actually consider hell as a place (or state?) in which everyone who does not accept Jesus as their savior will end up getting. They say God is just and cannot impose his love on us. So if we choose not to follow him, he'll not force his love on us. C.S.Lewis considers that hell's gates are locked from the inside. That means those who went there chose to abandon God and stay in their mindset. Other scholars would insist heaven and hell are the same place, it's just that the love of God is a bliss to those who chose him and a torture to those who rejected them.
Yet, the topic stays controversial. You have Adventists, for example, who believe in the ultimate reunification of God for everyone (so no everlasting torment).
Then there are respectable Christian scholars who'd insist that God's love will bring everyone to heaven sooner or later (Talbott is among them: https://www.amazon.com/Inescapable-Love-God-Second/dp/1625646909). He has also written this article on the Plato Encyclopedia of Philosophy, kinda the wiki of philosophy: https://plato.stanford.edu/entries/heaven-hell/
Anyway, as you can see, the condition for salvation for Christians (I am not saying for all of them, but from the articles I've read on the topic) is the belief in Jesus.
I am much less knowledgeable on Islam, sorry. A quick search makes me believe that salvation in Islam is achieved through developing and understanding the purpose of life as established by The Holy Quran, embracing Allah and leading a righteous life. It might be more complex than that, I'll let Muslims elaborate on it and I apologize if I got it wrong.
Now, if you want my point of view... I'd choose none. Why? Am I not afraid of hell? Of eternal punishment? Of course I am. And very much so. In fact, that drives my scrupulosity over the top. Don't I want the love of our creator? I guess I do, given he exists.
But if I choose to be honest to myself and aligned with my beliefs, I find no good justification for hell. To me, a loving God would not send anyone to hell. Nope, not even Hitler and serial killers. No finite sin, no matter how horrendous, should deserve eternal punishment. That is on the classical "sin side" logic. But even in the new Christian logic I've described previously some things don't fit. No, I am not choosing to alienate myself from God because I want to consciously reject his love. It is just that I am very skeptical. That's it. I've been incited to apply my critical thinking over and over in life. Why would God expect me to suspend on religious matters? Yes, even if he is great and created the universe and sent his son to Earth to die for us (what about all the mothers who have sent their sons to die for their country in the war? and nobody survived or got resurrected, from what I know), even then... could he not understand that humans, silly children, would refuse to acknowledge him? If my son were to tell me in his delusions "you are not my mother" I'd still love him and want him to be happy. My adoration for him would be stronger than my ego and I would not want him to suffer eternally. That is on the philosophical side.
Now on the factual side... Let's see what we have here. As I've previously mentioned, I have an inquisitive mind. So I started wondering what evidence we have for the resurrection of Jesus. This is the cornerstone of the Christian religion. So I went from thinking "he was a Jewish guy, quite charismatic and influential, who had disciples and maybe came back to life three days after his death" to thinking "actually, the guy has probably never existed or, if he did, he was so far from what we think he is". Most historians agree on a minimum set of facts about historical Jesus (resurrection isn't among these facts). But there are peer-reviewed scholars who think the guy was a myth. Richard Carrier is among them: https://www.youtube.com/watch?v=WUYRoYl7i6U&t=2608s
Carrier tries to estimate a probability for the existence of Jesus and, according to his interpretation of the existing evidence, it would be quite low (he does not say it's zero though). Just for the info, Carrier thinks that the evidence for the existence of Mohamed is even lower (he mentions it here when answering a question from a girl in the audience: https://www.youtube.com/watch?v=LTllC7TbM8M). So I've started doing my research on Mohamed too, but it's too early for me to give you an answer. The guy also has courses on his website for answering both Christian and Islamic arguments.
You might think "well, the guy is a crank, most historians at least agree on the historicity of someone called Jesus", but you should know that Moses too was considered historical, until more elaborate research has shown he's a mythical figure. But then again. You can pick the rational way, but you don't have to. Some people prefer to take the leap of faith. I personally am bothered that it is fear that pushes me towards religion and knowledge further away from it.
If I were to embrace any supernatural view at all, I'd be inclined to go for religions that include reincarnation. I don't have a strong stance on it, but I've read several cases (in fringe journals or random articles, truth be told, so there is lots of room for doubt) about accounts of children telling details from their past lives. But then again, more research needs to be done and many questions stay unanswered.
So there... you have my honest view on it. I have certainly learned a lot on my spiritual journey and I hope you do as well. Good luck.
P.S.: Now, from an OCD point of view... probably the best answer would be "do you think you are damned and lost? Maybe, maybe not". As you probably know scrupulosity is a beast in search for certainty. And you will find none, not in this area. So I am not sure my answer has helped you in any way or, on the contrary, has given you many new reasons to obsess.
The Inescapable Love of God by Thomas Talbott is a personal favourite of mine, and is both solid theology and easily accessible even if you’re not that well-versed in scholarly theology/philosophy. Another one, which I haven’t read myself but have heard a lot of great things about, is The Evangelical Universalist by Gregory MacDonald (Robin Parry).