Thats a lot of thought to put into a FWB situation. I don't judge as have been in 2 before. I enjoyed the fun and excitement but didn't think of them daily or muse or wonder about future. It was just a nice side addition whilst I was getting on with life in other ways.
I stopped when I met someone I wanted to be in a relationship with, and that developed. OH had a FWB when I met him too..he dropped her and I dropped my guy.
FWB - it is what it is. Its exciting, illicit, people say all sorts of what ifs or maybes, in my case particularly with one we went out and socialised a lot together etc and we talked a lot about life, day to day stuff etc. Still didn't mean that would necessarily make us more than FWB tho. We just got on very well
FWB with one wanting more than the other and/or the other person hoping waiting and wondering is a lot of potential for hurt. You may as well wait it out but also accept possibility that he doesn't want what you want and it may not end well
If a man wants you as a lifepartner, you know it - no messing. You won't have to wonder. Thats the difference. All the I don't know what I want stuff is a smokescreen -they do know what they want, its just not you..so you are either a FWB, or a placeholder. Which is fine, if you're cool with that.
You fit his mummy/son fantasy, I wouldn't find that sexually appealing but different folks different strokes n all that. Its holding you together. Try to enjoy the moment if thats your bag instead of trying to look into a future with him that he hasn't really offered you