Advice and opinions needed 😩

I would like to get some perspective on this.

So I’ve been with my SO for 5 years now and have been living together just as long. It’s safe to say he is my best friend.. he’s been nothing short of amazing to me and my kids. We have no biological children together but has taken mine in as his own.

I have a (6) year old son from a previous relationship. His father is not really around. He’s like that one uncle that comes around a few times a year and just pops up when he’s in town (although he’s just 20 mins away). He’s never really been a father to our son. My current SO has raised him with me since he was 2 and taught him everything he knows. Took care of him when sick, attended school meetings pretty much everything a parent is supposed to do, he’s done for him. He refers to him as “son” or “my boy”. A couple of years ago he told me he wanted to be his father figure but I kind of brushed it off... I guess he really meant it. I do consider us a family and people know us as such.

So here’s my problem: we are only boyfriend and girlfriend. Yes, we talk marriage and a future together, but that’s not the reality of the situation right now. There’s no real legal commitment. You can leave at anytime and disappear and that’s it. Men come and go.... I know he would be the type to forever be a dad to him even if we broke up, but the unknown and the possibility of him choosing not to, and breaking my sons heart scares me. As my little guy gets older he only grows closer to him...Although it warms my heart, it also makes me nervous and wonder if I’m making the right choice as a mom.

Should I limit this? Is it okay for him to take on the role of being his dad?