Good decision dropping him. I also suggest you stop creating free mock ups for clients. Let them use your portfolio, case studies and testimonials as a guide to your skills. If they want mock ups, they can pay for them - the mock up process is an important part of the project, it shouldn't be free - also it requires a lot of consulting to create a decent mockup, so you're either just banging out a quick mock up which will invariably fail to impress, or you're spending a lot of time on it, in which case the potential client is thinking 'wow, this guy does all this work for free, is he really worth the $xx per hour he's eventually going to charge me? Or maybe he's desperate?'. Is it any wonder the guy didn't feel like paying you upfront? He simply doesn't value your time at all.
I must admit, this is the first time I've ever heard a prospect request a revision on a free mock up. That's pretty cheeky
Anyway, best of luck - most clients are not like this, just develop the sixth sense to sniff these time wasters out at the earliest possible opportunity.