Matthew, maybe you can limit the amount of time you spend in the presence of your best friend's boyfriend? Make plans to see her at your place or some place out and about where he won't be. He sounds like a wanker and neither you (nor she) is likely to change that. Keep your chin up, you're doing great things for yourself and his snide comments should carry
no weight (
pun intended 
) with you.
I work really hard to maintain a positive attitude and I have no tolerance for people who are negative and mean-spirited. For me, pervasive negativity can be like a black-hole and can drag down my attitude (even if it isn't directed at me). If at all possible I cut people like that out of my life and if I can't do that (if they're a family member or a work colleague) I make conscious decisions to limit the amount of time I have to interact with them.
I know it is tricky when it is a close friend or family members' partner though.
Good luck!
****
I'm quite excited because I weighed in today to find that I lost an additional 1.2lbs last week... despite the fact that I had special weekend company; I went out to eat (a lot), I had more cocktails than I normally would have over the course of a long-weekend and I didn't exercise on my normal schedule or intensity level.
I had given myself permission not to fret too much about counting points or marking times of workouts, but I expected to see a gain or a hold-steady on the scale. 'Tis a pleasant surprise and means I've lost 5lbs total in the past 3 weeks.
I think that means that *for the most part* I was making good choices about what I ate and drank in terms of content and portion size.