I find it interesting that Former Friend lays all the blame at your feet, while still courting your BF. It takes two to make a relationship, doesn't it?
I have a friend like this, "Mike". He's weirdly possessive of another one of our guys friends, "Bob", to the point of having a man-crush on him. He's hated every girlfriend Bob's ever had, and even refused to acknowledge some of them. I'm talking about giving these girls the cut direct in social situations for no apparent reason. Then, when Bob starts pulling back from the friendship, Mike blames the girlfriends. Well, Bob's married now, and Mike has had to learn to play nice or lose his friend altogether. Unfortunately, the damage is done, and they're not as close as they used to be.
OP, I suspect it's going to be the same in your case. As your relationship progresses either Former Friend is going to have to play nice, or lose his friendship altogether. Of course, he'll probably blame you for that, but having someone to blame is poor consolation for losing a friend.