i know how hard this situation is. it's hard because if he doesn't speak to you, you'll feel like he hates you. and if he does, you'll read things into it. i've acted in a variety of different ways when seeing my ex - i used to be really friendly, and was then disappointed when he was standoffish and drunk and sarcastic to me. so instead, i reminded myself that we were exes for a reason, and took less notice of him. this was better, as i found he actually made more of an effort to talk to me, and i didn't feel like i'd acted overly nicely to him when he didn't deserve it. just be nice, calm and distance yourself.
and size 12 is a lovely size.