Wow. That sounds like a fucked deal.
Your initial post didn't have any elements of "hostile takeover" in it, but I always ask, just to be sure. That said, how much is "revenge" worth to you? (Hint: If it is important at all, first define "revenge," for you, and don't deviate from that.*)
If you want revenge, and you /can/ compete [successfully] against them, DON'T sell your customer list or sign any type of non-compete. But, since you suggested that you can't (or at least can't right now), selling your customer/client list, and/or a non-compete will buy you time and money (or, money^2, since time=money). The trick is to figure out how long you'll be out of the game, medically, and make it for that term. Broken back? Two years in rehab before you're presentable? Looks like a 2-yr non-compete to me. Make it as specific as possible; if an element (a material element) is broken, you're that much closer to being released from it.
Finally, since your livelihood IS in jeapordy, stop listening to people on the intarweb and get yourself a good lawyer (if at all possible, one who specialized in this stuff; even if only to "spoil the pot" and prevent your partners' ability to use him/her). Yes, he'll/she'll be more expensive than that $50 book that you referred to as "a little steep," but should provide an extraordinary ROI in the long run.
These are just things to run by your atty. Depending on the specifics of your industry, situation, and the laws of your state, these ideas may or may not be worth a damn.
* IOW, revenge is usually/often expensive, but mission creep is often exponentially more so.