Hate to say it, but it's time for a lawyer. Also, go to BBB, and the town's building dept. They may not be able to help, but they may help put the guy out of biz.

He's working on other projects. I surely hope you have a schedule of payments and didn't pay him it all up front. If you did, he will NEVER finish it without a legal threat over his head. Besides, at this point, if it were me, I'd want to be rid of him and get another contractor. Have your lawyer go over the contract. I doubt it's iron-clad and the law frequently allows for unwritten definitions of reasonableness--like a reasonable time to completion or requirement to explain why. This guy has your money and won't talk to you because he wants to keep it and not actually have to do work for it.

It is a problem in ALL the trades. Our kitchen was supposed to take 6 weeks from demolition to completion but took 6 MONTHS and I ended firing them and completing it myself.

I will NEVER have a project done without a SUBSTANTIAL final payment--1/4 to 1/3 of the total will not be paid before completion. I learned my lesson!