How to make a graceful getaway from a nightmare boss?

In January of last year, I got ran out of Portland, OR, and wound up staying with some old friends in Tampa, FL. An old roomie of mine had a girlfriend whose father was redesigning a mansion, and was convinced to allow me to work on it for a bit of cash. After a while, he stopped paying me, with promises of paying me later. I couldn’t find work elsewhere, as I don’t have a car, and Tampa is built for cars, so I was convinced to go forward on a plan to live in the house and work on it in lieu of rent and utilities, with him controlling what we eat.

It was a stupid move. Everything I do, think and am he and his wife condemn and ridicule. Still, I had nowhere to go, so when we neared completion in July, He offered me to work on his mansion in Milwaukee, WI, for a little while, with pay. I accepted, as this would be getting me closer to Portland again. He took half of my valuables to Wisconsin, and we stayed in the mansion in Tampa until September because a thousand other things were pointed out by professionals that we still had to do (my boss in an accountant, not a carpenter). He brought me to his mansion in New Jersey, and stuck me in the basement without heat, gets mad when the 2.5 protein-poor meals I eat a day aren’t enough (even though his pantries are so full stuff fall out of them), and expects me to continue with the plan to live in and restore his Milwaukee mansion in the dead of winter, with the plumbing, heat, and gas lines all destroyed by one of his idiot friends, WITHOUT PAY OR PROSPECTS.

It was a stupid move, I know, you really don’t have to tell me.

So some questions remain: I hung on this long because they charmed me into giving them my word, and my word is law to me; but my word isn’t worth this. Still, this is a bridge that will burn when I cross it.
How do I gracefully leave all this after I’ve given them my word? Is it even possible?
How do I explain to employers what I’ve been doing for the last year?
How do I keep them from sabotaging any future work or prospects through slander or somesuch?

Your help in undigging this hole is greatly appreciated.