I think I would be tempted to tell him he has the paperwork back to you by the end of the day Monday, or he will be served before the end of the week. Leave him a voicemail, email, text, whatever. It only takes a few minutes to get the acceptance notarized, he can do it without a lot of time. If he doesn't, then make sure you follow through. He doesn't respect you. Following through like this will perhaps make him realize that he should.
Otherwise, it's another three weeks, and who knows what excuses he will come up with then?
