You’re in denial. It is understandable. He has broken a covenant with his affair. You’re denying how the physical affair hurt you and focusing on the pictures. IMHO, masturbation is normal. Your husband Masturbating to pictures of your family members is batshit crazy.
He wants to alienate you from them by seeing them as rivals for his affection. By doing this he is saying you “aren’t good enough” and he needs sexual stimulation from sources external to the marriage who aren’t you. You didn’t sign up for this. It’s totally creepy on a variety of levels. I’d speak with a lawyer about your options, there are two good books at Amazon:
https://www.amazon.com/Detach-Survive-Self-Care-Midlife-Crisis-ebook/dp/B007XUDJVW
https://www.chumplady.com/book/ Leave a cheater, again a Life
Good luck and I’m sorry.
Tina Swithin has written great books and blogs about HC spouses, and how to deal with divorce and child custody issues. Here's just 1 of her books that's free with an Amazon membership.
Divorcing a Narcissist: Advice from the Battlefield https://www.amazon.com/dp/B00IPKV3UI/ref=cm_sw_r_cp_apa_d-rkBbM0C7CJA
I hope you check out all her work and her blog, they definitely help.
Du machst das ganz richtig, du mußt dich jetzt erstmal selbst schützen, bevor du auch noch Schaden davon nimmst. Das meine ich nicht nur auf physische, sondern auch auf die psychische Gewalt bezogen. Das völlig paradox wirkende Borderlineverhalten kann auch Angehörige kaputt machen, wenn man sich nicht dagegen wappnet.
Falls du denkst, dass es dir helfen könnte darüber zu lesen, gibt es ein ganz gut bewertetes Buch dazu bei Amazon. Ich habe es nicht selbst gelesen, weil ich nicht direkt betroffen war oder bin, aber ein Freund hat eine Trennung von einer Borderlinerin hinter sich und das nagt immernoch an ihm.
Alles Gute.
Have as much as possible of a complete and stable plan for them ready to be laid out BEFORE you tell him. "May" need to sell the house is not something you want to tell him. Either you're going to sell the house or you aren't.
If it is in any way possible, get as many details of the divorce laid out in advance before telling them. Figure out custody/visitation, where each parent is going to live, etc.
Then, honestly its the same-old, same-old "Mommy and Daddy both love you guys SO VERY MUCH, but we don't love each other anymore. Sometimes mom's and dad's fight a lot and decide it is better for them not to be married anymore. That is what your father and I have decided is best for our family, for mom and dad to live apart. You're going to spend X days here with me, and Y days with your father."
Allow them to ask questions, and answer them in an age appropriate way. If you aren't prepared to answer the question, don't be afraid to tell them that you don't know, or that you'll get back to them on that after you think about it.
Pick up a few books from the library about how to talk to kids about divorce, or honestly just google for some articles. Here's a suggestion from Amazon. This google search alone comes up with a ton of good articles about what to say/what not to say. How to answer questions, etc.
When my husband of 22 years dropped me and our daughters via WhatsApp, a few months after professing his eternal love and how he was nothing without us, I was devastated and incredibly angry. I found No Contact the one thing that kept me sane through my terrible breakup, that, and writing a book about my side of the story and how I recovered and found love again. If you want to read it and you think it would help you, you can download it from Amazon for free. It is called: "The Good Breakup, take a deep breath and remember who you really are"https://www.amazon.com/Good-Breakup-Breath-Remember-Really-ebook/dp/B07NNXH8GN/ref=tmm_kin_swatch_0?_encoding=UTF8&qid=1553334322&sr=8-1-fkmrnull