You can get cheap remote starters for around $60, that's about the price of a FB.
1: From from instantly to forever. You can chip a tooth almost instantly.
2: No, you can damage the starter and flywheel
3: At a shop? I'd guess $600-$1200 depending on the car. More if you damaged the flywheel
4: There is a "neutral/park safety switch" wire that should let you do just that.
I wouldn't use the FB to start your car. Say the computer locks up in the middle of starting? That's up to and over $1200 because oops, your computer hiccuped.
Edit: my bad, cheaper: http://www.amazon.com/Design-Tech-De.../dp/B0000DEZK1
I'm not saying you shouldn't get a Fusion Brain, it's an awesome piece of hardware especially for the price. But I would not suggest using it for a remote start.