>>1 Although I'm not a therapist, I'm pretty sure that you do not have MPD. It's not a, "black out;" you just forgot why you were in the room. It happens to all of us. Literally. Everyone forgets pieces of their childhood, some more than others. Most people change how they act (intentionally or unintentionally) depending on who they're with.
Feeling "unreal" is kind of... eh. You need to elaborate on that one.
Voices in your head is a bad sign - you may be dellusional and should get it checked out, but it's not a sign of MDP.
It's normal to forget things you've said or done. Some people have worse memories than others. I'm in the same category as you are where I can forget things from just a few moments ago. I can forget what I did the entire day. That's a another reason why I like computers and planners - I can always go back and verify what I was doing.
With the insults, a lot of people take completely normal comments as insults. Those are sensitive people, and I have the same problem, especially when it's someone that I don't really care about; I'm not going to bother remembering what I said to someone I don't like.
MPD is much more extreme than the things you're talking about, as far as I know.