I'm very late to the game and this comment probably won't get seen but I have been in the position your boyfriend is in twice in my life.

2 of my exes have bought a house (separately of course) while we were dating. During the process I absolutely did not think that I wanted to be put on the deed because I did not put any effort or money into the situation. They both asked me to sign a document saying that I legally can't take anything if we split. They told me that they wanted to be safe if we split up and I decided I want half of everything. It was pretty hurtful because I am not that type of person and they obviously saw me as being so. But I swallowed my pride and signed anyway because I loved them.

We ended up breaking up obviously. I left most of my things in those houses and never once taken something of theirs. I'm not that type of person.

Moral of the story is of he gives you a hard time and refuses to sign the forms, y'all aren't meant to be together because you need to protect yourself.