You own the moral rights to your work. You may be able to exercise those rights under the copyright laws of your country. Furthermore, if this contractor is illegally pretending to be an architect, that puts him in a precarious legal situation. He's defrauding his clients.
In my country, if plans get signed by a fake architect, that puts everything else in question, the permits, the insurance, the loans from the banks, etc. So not only that puts him in a precarious legal situation, but that puts all his clients in a very precarious situation as well. Of course, this is assuming that the plans in question do require an architect to sign off on, not all plans do.
You may want to consult a lawyer on this issue. He stole your moral rights to your work. He owes you damages on the existing plans he stole from you.
If he really wants to profit from your plans, that's possible, but he should become one of your affiliates, not steal from you or defraud his clients. In an affiliate program, you can promise him a commission on the revenue that he brings in for you, and you can even promise him future residuals on repeat customers that he originally brought in for you. That would be the proper way and legal way to do it.
Ultimately, I really think you should consult a lawyer on this. If it can be proven that you learned about his fraud at some point, but kept on knowingly selling him plans after that. You will be perceived as a co-conspirator and not just as an innocent victim.
Should I confront him?
That depends. Is he really a fake architect? If he's truly a fake architect (in addition to having plagiarized your work), I wouldn't confront him. The harsher the punishments he's potentially facing, the more he may try to threaten you into not reporting him.
In a case like this, it may be in your interest to report him to the licensing board and to the authorities first.