It sounds like the wife may have made the situation worse by misquoting you. And he believes her and that hurts. I would write him a letter and tell your former master your honest feelings but do not blame the wife. (maybe give him the letter in person so it doesn't become intercepted) That would just come back on you.
I thought once I could not forgive my master. My master gave me the art and I respected him greatly once but in one month he destroyed that respect. But since my master is lately, also trying to make amends, I will try too. I had to forgive him, and I did that finally for myself because I can't hold that bad feeling inside me, so I freed it and disowned it. I doesn't make what he did better or excuse it, it just stops the pain of it. I don't know what your master's problem is, now, that he mistrusts you but apparently it meant alot to him that you turned from the art that he taught you otherwise, he wouldn't have bothered seeing you. If the wife is planting bad seeds in his ear, maybe it is her that doesn't want him to be teaching or in MA anymore. The MA have a large divorce rate, so that is something to consider. I would be devastated too if I couldn't continue Taekwondo and was for the fact that I had hope. But without hope...I could see it would be so much worse. And, if his best student turns away and goes to a different art, that would hurt too, because that is all he has left, his legacy and that may be you. I may be wrong, but I feel it may be a misunderstanding. TW