This is the one we have. His favorites are the hot chocolate breath and the color breath:) link
So sorry to hear you were abused and had similar anxiety experiences as a child - but also glad for your daughter's sake that she has such an understanding parent helping her work through this!
Here's what I'm thinking... she needs a total "reset" on bedtime. It sounds like maybe there was originally some separation anxiety going on, but now it has escalated to the point that even just the idea of bedtime is terrifying to her. Just experiencing those meltdowns, feeling so out of control, is scary in itself for a young kid, on top of the original fears that triggered them. So I would start by focusing on what will make her feel safe enough at bedtime to prevent a total meltdown. It's tricky because you don't want to set up bad habits that will be hard to break later (like, I wouldn't recommend letting her sleep in your bed, because that could be really tough to "undo"), but at the same time you do want to cut her some slack and know that this modified bedtime routine won't be forever, it's a stepping stone toward getting back to sleeping more independently.
Is she able to talk about the bedtime issues during the day when she's calm? I know for me, as a kid I was so embarrassed by my out-of-control behavior (probably in part due to the way my parents shamed me for it) that I never wanted to talk about it, just tried to deny everything during the day. But I'm hoping your daughter might be more open to talking about it and problem-solving with you. If you said something to her like, "I can tell bedtime is really scary and upsetting for you lately, and we want to figure out how to make it better. Can you think of anything that might help you feel less scared and sad at bedtime?" -- do you think she would be able to engage in that discussion? You want to emphasize that you're on the same "team" together, that you want to help her with these big feelings rather than just getting her to be quiet and go to sleep. Kids are really perceptive about that distinction, I think, and just knowing that you're on "her team" and trying to solve this with her can go a long way.
I think engaging in that discussion and really listening to her, trying to empower her to be part of the solution, is an important first step. Even if her ideas are unrealistic, try to find a compromise and explain why you can't do exactly what she's asking for, but that you want to do as much of it as you can. If she doesn't have ideas, or if you want to guide the conversation a bit more after she's had a chance to share her thoughts, you might suggest that you or your partner can stay in her room until she falls asleep, talking through any big feelings she's having, until bedtime becomes less scary for her. It sounds like you may have gotten into a cycle where the only way she can be sure you'll stay with her is if she has a meltdown; even if she's not consciously thinking, "I'm going to have a meltdown so mom/dad won't leave me!", that may be what her brain has learned on some level. So you want to disconnect those two things, let her know that you're going to stick around anyway, and once she becomes secure in that knowledge I suspect the meltdowns will start to dissipate and you'll be able to work on better coping skills for her to deal with her anxiety.
Making some other changes to the bedtime routine might help with that sense of "reset" too - in particular, I'm thinking you could add something for her to look forward to after "lights out" that could kind of replace the meltdowns (which have unfortunately become almost part of the routine, in a way - her brain expects a meltdown to happen next, so it becomes kind of a self-fulfilling prophecy). I'm thinking something like a cool nightlight that projects stars on the ceiling, or a kids sleep meditation that you listen to together, or even an audiobook of a favorite story that she can listen to while she falls asleep. There are also some great books of kids meditations and mindfulness activities you could try working on with her during the day (though it might be a while until she's able to apply them to a high-stress situation like bedtime) - I recommend Breathe Like a Bear, Mindful Moments at Bedtime, and the Mindful Kids card deck. You could also check out some relaxing bedtime stories like Sweet Dreams: Bedtime Visualizations for Kids and The Sleepy Pebble and Other Stories.
You may want to be cautious about anything that seems too focused on making her fall asleep though - that in itself may actually create more anxiety. Emphasize that bedtime is about just relaxing quietly, NOT about any expectation that she has to actually sleep - her body will sleep when it's ready. And as much as you may want to expedite the process so you can go to bed, right now the important thing is getting her comfortable enough in her bed to let her body relax; at first, that might take hours, but at least hours of sitting quietly with her listening to meditations or watching stars on the ceiling is preferable to hours of screaming...
Hope something in there is helpful - please keep me posted on how it goes! I'll be thinking of you and your kiddo!
There are lots of great resources for teaching kids mindfulness and calming tools! Check out Breathe Like a Bear for a variety of different calming activities based around different animals; Alphabreaths for deep breathing ideas inspired by each letter of the alphabet; and Mindful Kids, an awesome card deck of mindfulness activities. If there seems to be a sensory component, you might also check out The Kids' Guide to Staying Awesome and In Control.
Are you in therapy to work on your dissociation? The best thing you can do for your sons is to get help for yourself - put on your own oxygen mask first, so to speak.
In the short term, you might try to find activities to do with your boys that require active engagement from you, so you can't get as lost in your head. Tossing a ball back and forth is something I find to be very grounding, for example. Physical interaction, like giving them piggy back rides or balancing them on your legs, can be grounding as well. You might even look up some fun parent/child yoga ideas. Being outdoors together and focusing on sensory experiences, like grass under your bare feet or water running through your hands, can be both grounding for you and fun for them. In fact, you might look into some kids mindfulness activities, which would be great skills for both you and them to practice! Your 2yo might be a bit young, but you could start with a book like Breathe Like a Bear or Mindfulness for Little Ones.
Congratulations! Here are links to a few books and games I use regularly with my younger students as a school social worker:
Breathe Like a Bear: 30 Mindful Moments for Kids to Feel Calm and Focused Anytime, Anywhere https://www.amazon.com/dp/1623368839/ref=cm_sw_r_cp_api_glt_fabc_07MGT2408RTGRMCVF530
What Should Danny Do? (The Power to Choose Series) https://www.amazon.com/dp/069284838X/ref=cm_sw_r_cp_api_glt_fabc_Q48MV1HR59EGMCPV2J6S
Listening to My Body: A guide to helping kids understand the connection between their sensations (what the heck are those?) and feelings so that they can get better at figuring out what they need. https://www.amazon.com/dp/099895800X/ref=cm_sw_r_cp_api_glt_fabc_6GGT5RGPTHDBYFBWTZN1
https://www.childtherapytoys.com/products/the-stop-relax-and-think-board-game
https://www.childtherapytoys.com/collections/best-sellers-games/products/the-impulse-control-game
https://www.childtherapytoys.com/products/remote-control-impulse-control
https://www.childtherapytoys.com/products/remote-control-worry-control
Also recommend the book Breathe Like a Bear and the app Stop, Breathe & Think for Kids, which both have some great simple meditations.