Thanks for the comments
I'm pondering everything that's been said, so I'll address some questions and clarify some things now but I'm not ignoring anything else that's been said!
RE moving in: We're certainly not making concrete plans at this stage, or talking about living plans all the time or anything like that. We've only really discussed this because we wanted to be on the same page about the possibilities of where this might end up. It was certainly never set up as an ultimatum or anything like that (to reiterate that Bob isn't pressured into something he doesn't want to do) but we talked about these things early to get an idea of where each of us would be comfortable with the relationship heading in terms of life entanglement.
RE Anne's other relationship attempts: In the time I've known her she's had two people she has been excited about getting into a relationship with, had a bunch of dates within a couple of weeks and then it has broken down for some reason. While she might have a different, more relaxed, relationship development style than me, from what i have seen she would happily get into deeper relationships quickly if the right person came up.
RE my polyness: I'm not really all that experienced in poly, for certain. I have been involved in open relationships for many years but polyamory is newer - not through lack of wanting it per se, but because it hasn't come up. I have another relationship apart from Bob but it is far more casual. I am definitely open to another relationship (would welcome it in fact) but really, I've met most of the local openly poly people in person and on OKCupid and I haven't clicked with any of them - relationships don't come easily to me.
RE interacting with Anne: I agree, I probably should assume intentions less. When it comes down to it though, I don't have the energy to maintain interactions with her any more. In general life, I would never be friends with someone who spoke to me like she does (regardless of intentions), and I would be far more forthcoming with telling them that they were offending me, but I've been civil because of our situation. It's draining as all hell. Sorry, this last bit was a bit venty. I've been trying not to burden Bob or our mutual friends with discussing this because it's not fair to put them in awkward situations like that.