You asked some very good and important questions. Thee are no direct and / or simple answers to them.
First of all, I don't want to call myself a full-time trader just yet. I do call myself a daytrader. I have been doing it as my main source of income for a couple of years. If things continue to go as they've gone over the past 18 months for another couple of years, then I think it would be fair to call myself a full-time daytrader.
Quite frankly, I believe that to a large extent, my profits / success are related to the size of my account. It's like anything.... The more money you have, the more money you can make...
I won't get into my personal finances on this forum, although feel free to PM me and I could certainly give you more detailed info that way. We could discuss the issue of leverage vs. account size etc.
Forex trading can be the most exciting financial avenue one can get involved in. It can be one's biggest nightmare and can also be one's biggest dream come true. I know that only a small percentage survive and only a smaler percentage ever make big money at it.
Again, feel free to PM me and we can discuss these things.