Mwalsdor, I think you are correct in wanting the signal lead to be silver in your SET configuration. I also think that the 22 ga. was the proper size for it.
Regarding the manufacturer, he accepted the deal, and did not carry out instructions. He should make good, if for no other reason than good customer relations.
I would take this route. Contact him again and ask him to rewire the unit in the way specified. If he refuses, that is strike one. Then ask him if he will pay at least some portion of the cost of having someone else re-wire it. If he says no, that is strike two. Then ask him if the warranty will be valid if you have someone else re-wire it. If he says no, that is strike three.
Three strikes and he's out. He made a mistake, he won't fix it, or pay to fix it, and he won't warranty the fix. If this happens, I would not have anything to do with them again.
However, if for some reason, you don't want to press this issue with him, you can forget about it. Personally, I would be very dissatisfied with that result(meaning primarily the service question). If a resolution cannot be agreed to, get the service schematics and part # info on the unit, so you can get it serviced properly by your favorite tech, or yourself.