Generally it is best not to talk about the past. Of course if there are things about you that you feel that he really needs to know to understand you, then clue him in. Other than that, treat it as a need to know basis. If he doesn't ask, don't tell. Any new relationship should be treated like a new beginning.
Better than letting them find out on their own and then feeling you didn't trust them or were trying to hide something. I don't mean give them a list on the first date, but if things start to get serious, be honest.
Yes, but do it tactfully and only do it after you're sure he is interested in you.
No. Will it change anything? Since it won't, don't mention anything.
Not as much as your present ...