3. I need to repeat this process:
a. Get bitcoins into bitfinex
b. Transfer to Mt. Gox etc.
c. Convert to USD - make profits
d. Use USD to get more bitcoins
e. Transfer bitcoins to bitfinex again
f. Repeat
Your steps don't make sense. Transfer BTC to bitfinex, then transfer it to Mtgox, then convert to USD, then convert back?
I think this is what you mean:
a. Transfer USD to bitfinex.
b. Buy BTC on bitfinex.
c. Transfer BTC to Mtgox.
d. Sell BTC on Mtgox.
e. Repeat.
Anyway, you are certainly not the first to come up with this idea. There are probably a hundred posts just like your in this forum alone. There are even websites and bots that do this. The reality is that there is a big spread because nobody is able to take advantage of it, even though plenty of people are trying. Do some more reading to find out why it doesn't work.