No, wrong. Your point of exit should not ever depend in where you entered or how much you made since then. The market doesn't know where you got in, so how could it influence your future expectations?
Yes i do this, I have done it a long time. Your software should have a feature that puts all $$$$$$ to cover the P&L.
always. while my system is automated so watching it doesn't affect my trading, it certainly has the ability to reduce my productivity. i still catch myself taking a peek more often than i should