I have nothing constructive to add to your predicament but I had a similar experience with a local dealer myself. My first NFA purchase from a dealer almost turned me off to the whole process but thankfully the issue was resolved. I know how frustrating it is doing business with an unscrupulous dealer, only to find out as such when it is too late. Sorry about your ordeal and I hope it is resolved soon. NFA is a small world and word of mouth regarding crappy dealers will surely ruin his rep in the business....
Silencers have NEVER been illegal !