Some of you may know my backstory, but to summarise; split with XP 7 months ago, we have a 13mo DS who lives with me. XP refuses to have a routine as he works unscheduled hours, and as I am currently a SAHM on benefits, he sees DS as and when he is not working - a couple of times a week, inc. overnight when convinient for XP. (I know this situation is far from ideal...)
Anyway, XP has moved from 1 temporary flatshare to another as cannot afford to rent a place of his own. But he is now looking at buying, with help from his parents. He is looking at some of the HomeBuy schemes and has said that for some of them, in order to be elegible for a 2 bedroomed place, he needs a document to say that we have shared residence of DS. Although, he says, we ''wouldn't really, things will just stay as they are''. 
He also said that when DS gets to school age, then we can discuss whom he will live with/where he will go to school (we live about an hour apart, so will have to be one or the other) which makes me feel like retching quite frankly, but am trying to keep my personal feelings out. Can you even do shared residency with this amount of distance?
I would like XP to be able to provide DS with a stable home with his own room, but can't help but feel I would be getting screwed over somehow if he gets a document to say he has joint residency, yet continues to see DS as and when. I would like to add I am not opposed to doing 50/50, if we were to actually do 50/50 but feel DS is currently too young, and obviously as I said, logistically we couldn't do it with school anyway...
What are your thoughts? Please talk some sense to me as am currently bewildered and find X intimidating and manipulative