If your contractor walks out, move your project along: Get it finished and don't rely on suing to recover your cash. That's the reality-check advice on Brownstoner.com.
"You are wasting your time thinking that you can get $100,000 in damages..it will be reduced to $3500 by a decent lawyer," says one commenter. Moreover, adds another, "The GC may not have any assets to compensate you with even if you won."
Still, you should probably check with a lawyer about whether you lose a anything by not pursuing the miscreant contractor now. If the decision to sue or not can wait, document everything and then focus on completing the work.
One thing a lawsuit can do (if you decide the effort is worth the expense) is to "get a court to solidify what damages above the amount of the contract are owed to you"--what it cost to fix the mess, in other words. You may then be able to write it off.
Note to future renovators: Depending on the size of your job, it might be worth doing a background check on a contractor before hiring him. The price to do a thorough check of litigation and liens against a small 2-5 person outfit is around $2,000.