Should I continue to fake it to make it? Or tell him the truth and ruin everything?

A few months ago my fiancé and I were looking to buy a house.. I was (and still are) a stay at home to our 4 kids (2 his, 1 mine and 1 both) when one day he came home drunk, didn’t know I would be there, and shoved me.. I called the cops.. DUH.. btw only the youngest was there.. she was about 6 months at the time.. well he went to jail, got out after a couple weeks and is apologizing and what not.. I don’t even care honestly.. I’m completely done.. well because of this we lost the home we were meant to buy and the house we were living in, because we ended our lease.. so I’ve been living with friends, family and in hotels.. when he got out he started giving me money and paying for the hotels.. and now we are about to get a cheap little duplex on month to month before we close on the house.. it was my understanding from the beginning that it would be mine and the kids.. that he wouldn’t be there at all! Except to visit with his daughter.. his 2 kids are living with him... but my son’s father made it very clear he isn’t allowed around my son at all anymore.. and I don’t even want him around anyways.. but the other day he came to visit our girl and we were talking about the house and I brought up that he can’t be around and he said “oh, so I’m buying a house for just you???” And I said well yeah!! Duh! I told him if he ever wants to get back together he needs to go to rehab, counseling, and we need couples counseling but even then I’ll most likely lose custody of my son!!! And I’m not going to fucking do that!! I’ll die before that happens!! I feel like I was very clear from the beginning and he really thinks he has a chance to fix this.. my plan was to get the house, get a job, save up and get the fuck out completely!!! But if he knows I’m doing that I’m afraid he will end it all... I feel like I need to place nice to give me time but maybe I should just not? Thing is, how would I pay for daycare? How would I pay for food and life itself? I tried to get government assistance and they basically said he needs to be on child support before I can get assistance and my sons father.. but my sons father and I have a specific agreement to where he doesn’t have to pay child support!! And my ex fiancé is paying out the ass for me to just live and take care of the baby! So that would take months!! The fact he thinks him buying this house is going to make me stay with him and that he can just come and everything be good, makes me want to just say fuck it! Don’t do it! But I will be homeless, in a shelter.. then my sons father would get custody... and I’ll be without not only my son but my 2 bonus kids who I adore!! This is so hard.. I need advice

EDIT; his kids and him are staying at his moms.. they all have their own rooms.. she hasn’t even asked about how her granddaughter and me are doing at all!! He even admitted he lied to her just so he can have a place to stay.. I’m not worried about him at all and frankly idgaf if he had to sleep on the street for my kids and I to have a stable place since he promised me stability! I quit my job to help him! And to raise the kids.. now he is comfy at home with mom while I don’t know where I will be living.. having the house would help me get on feet.. it will be in his name until he deeds it to me (as he is promising) but I don’t believe him.. he will pay for everything and expects me to help him with the business and take care of the kids.. but he can’t be there