My lesson from when I was self employed (learnt the hard way) was if they are unable to pay what they owe you on time just go for the juggular, (i.e. the small claims court). I was way too soft on one customer, kept getting excuse after excuse, eventually getting a cheque (it was that long ago) that bounced, and shortly after I eventually started court proceedings they went bust & I ended up with nothing.
I like to give people a chance, but I think you've gone beyond what anyone could expect in accepting this crap from him.