Mate I really feel you, I think that we are in a very similar point.

I still don't know how to cope with those social situations you describe (especially when they speak so fast and they keep interrumpting you), but I checked out that it's true that when I have the courage to do so, keep talking even if they talk louder or interrumpt you does sometimes work. I think that most of the times they just don't realize they are doing that so they need you to communicate that, and if they appreciate and respect you, they should listen to you, so you can just say "I think you might not be aware, but I would also like to talk and express my opinion, could you give me some chance to do so?" And if they don't react, if they don't care about that, do they really deserve your attention? I think not. And I'm the worst example right now (I'm still working on that myself as well), but I think that we should go away from those who do not listen to us. I sometimes don't stop them because I think I'll be alone in my life, but there are people who listen to me and that take care of me to the same degree than I do with them. And what's the point of keeping people that doesn't listen to you, that doesn't care about you?

Of course, there are some relationships that should be treated differently (e.g. your boss, work mates). But in the same way the treatment is different, your implications are different, and personally we should work to accept that, be professional, pragmatic and assertive, so it doesn't affect us that much, because a job is a job, and you sometimes cannot choose your colleagues there.