[jd]

Additionally, if you're willing to go to the dark side...

If he's independently wealthy he probably has a lot more to lose than you do. You can use this as leverage. If you can get him in a position where he may lose a lot then you can probably get him to back off and drop the lawsuit.

So be willing and prepared to fight dirty (but still get a lawyer). He's bullying you, and against bullies it's often a good strategy to escalate beyond the comfort zone of the bully. He can afford to sue you because he doesn't feel vulnerable; losing the lawsuit isn't the end of the world to him. This is what you must change. Find a way towards mutually assured destruction.

If he's just a bully he's very likely to back off if you put up a fight.

[SoftwareMaven]

I wouldn't consider counter-suing in this case to be the dark side. In fact, it may be the best way to get legal representation with little out-of-pocket spend, since the lawyer could work off a percentage of the potential damages.