Yes the 5 year rule is quite correct - after project approval you have 5 years to build it and get it signed off with habitation certificates (living permission as we call it). Once 5 years has lapsed you need to resubmit the project with full plans. You can see how strong the architect is and why they generally get paid - they are like the mechanic who can trust everyone because they hold the customer's car. Upset him and you won't ever win, and it sounds like he has used his power after not being paid.
I'd once again recommend Ozlen Ozergin, she has handled similar situations at my request and is something of a property law specialist these days. As I said earlier, the rules that are coming into effect are genuine and you need to start doing something now or things will get worse.