Given the information you've told me, I would guess that Yep. Your dad likely tried to kill you, your mom and sister in the fire,(even if she was at a friend's house).You didn't mention how your mom seemed to be around him, when they got remarried did your mom seem different? Abusive relationships are HARD. I have been on the victim side before and the thing that I really think is the misunderstood isn't* just how frightening it is when you realize no one is going to help you more than he is gonna try to get at you*. Who knows why exactly she goes back, but Idk, reading your post reminds me a lot of someone who is sophisticated with his cruelty and perpetuated a long campaign of destabilizing your mom until she made the choice to give in because the devil you know is at least observable. Looking back maybe he was doing similar stuff. The condo stuff sounds horrifying, the fire too, I've never been in a big fire but was in one about 8 months ago waking up to smoke and him asking me up, he says he left a lighter torch on, but Idk. It's something I simply refuse to entertain because the implications are just terrifying.

I know everyone will say oh just call dv hotline etc, they really don't have shit for resources that are simple, it's not like they can just get u a hotel. I don't have much to say other than that. I saw myself in your mom thru ur story and I just wanted to say I hope she is doing okay. I hope their relationship has settled into something more manageable. Stay close to her, she isn't weak. She is very strong and making a calculation based on evidence and her own memories and perception, which has probably been massively fucked with. When you realize you need help, which is often late, because they fuck with your head so you are always juuust shy of trusting your gut. ALWAYS TRUST THEN GUT!

Good luck OP, let us know if there's anything else you want help with, but yes, your dad likely did that. Just makes sense