I want to think like this but maybe its wishful thinking. She said she decided not to go to the pub because of him- it would have been the perfect opportunity if she was interested? I was surprised on how aggressive he was about me, and her telling me too. Its a weird mix of feelings. I just am not sure what to think. Is she interested?
Well, there are a few possibilities here.
A) This may be the most likely - Women love to feel desired and it could make your wife horny, being hit on so directly and aggressively, where it had to be pretty clear to her that guy wanted to fuck her, even if she doesn't actually like the dude or want anything to do with him. Thus, she avoids further contact with him in a social setting and heads home but is horny and wants to jump you.
B) She thinks the guy is a dick but she is kind of turned on by his size, assertiveness and how direct he was in his desire for her. Maybe she secretly would like to fuck him. and when I say "secretly" I mean this may even be a secret to her... because, that's just how women are lol - However, if your wife is on the less impulsive / more prudent side, she also will consider that if this guy came on so fast and strong to her, he probably does that a lot and she might feel cheap and used if he fucked her once and moved on. She would also no doubt be battling with guilt. She stated that she felt guilty in her prostitute dream thinking of you, so that is surely a factor here as well. It's possible she was tempted to go out afterwards but declined because she knew the guy would hit on her more, in an environment with alcohol, where maybe something might happen that she would feel bad about.
I think it is interesting though that she told you everyone went to the pub afterwards but she decided not to because of that guy - it may be that she is looking for you to encourage her and suggest she should go next time, maybe just by saying "don't let that guy ruin your good time, go if you want and have fun, enjoy the compliments, I'm not threatened by him coming on to you."
Reading back to your original message, I can't help but wonder if your wife is kind of providing openings here for you to encourage her. She kept saying "swinging is weird," which really seems like a timid way of showing interest and maybe waiting for you to provide a counter-point if you're open to it, which you did, and then she brought up marriage vows - it sounds like she may be waiting for you to help her through her hang-ups. You should have followed up with something like - well, how is it against our vows if we both consent to it and do it for one another enjoyment?
Then she tells you this dream and says it was hot for her but she felt bad about it... you could easily read this as a woman searching for your reassurance and support.
I think the idea of doing something like this is very scary for women and no matter how many times you say its hot and you're okay with it, they will still have some lingering fear that they may do something and you won't like it and it will jeopardize your marriage, which is way more important to them than random sex, however the idea might arouse them.
If things ever did move forward, I think your wife would need to feel really sure that it is something that was going to please you and increase your desire for her. One thing you could do to build toward that is get a dildo, if you don't have one, and bring it out one night, telling her you would really get turned on watching her use it. The thing is to get one with a suction-cup base and stick it on the bed's headboard, then have her back on it and fuck it while you stroke your cock and tell her how hot it is. Note, you need a long enough dildo that she can get a decent amount inside her with her feet pressed against the headboard (I have experience with the engineering considerations involved lol). The first time you may not want to say anything about it being another man's cock - sometimes it is best if it is just implied as many women are creatures of subtlety. You could say things though as you stroke your cock to her performance like "its so hot watching you take that cock" implying, she is taking a cock that is not yours but without overtly making it about another man. It would probably also be really hot for her if, after watching for some time, you tell her you need to have her and its your turn now, then passionately fuck her until you cum. Afterwards, hold her and tell her how much you enjoyed it.
Another good one is doing a 69, where she goes down on you but you use the dildo on her - again, its a situation where you don't really have to say much, she's sucking your cock and there's another one in her pussy, it would probably be hard for her to not fantasize about getting spitroasted by two men.
Afterwards, you just tell her how hot that was for you and ask how she liked it. She may say she liked it because you liked it - its the safe response for a more reserved woman. It may also be true, who knows, but its really obvious my wife is highly aroused by doing stuff like that and I don't think it is just because it turns me on but she is always coy about it. In the past, when I've really pressed her, she has admitted to being turned on by some pretty dirty things but I think she is embarassed about it and prefers the silent acknowledgement that I know, that she knows, that I know what she is in fact getting turned on fantasing about taboo dirty .......
P.S. don't try to do this stuff every time you have sex or she'll start thinking you need it for sex to be exciting, its all your sex life will be from then on... you need to spread it out. It's best reserved for nights when you've gone out, had a couple drinks, been romantic and gotten her juices flowing in advance.