She said he was mortal enough for her. Mab cannot utter a knowing falsehood. She didn't say he 'would be mortal', she said, 'is mortal'. That means he is already, as is, mortal enough to qualify to be Winter Knight.
Does it? Remember why you should never bargain with the Fae! They never can be trusted! And what is the foundation of trust? Truth! In my opinion the point missed repeatedly by mortals is they fall for the Fae cannot lie line. The Fae cannot lie, but that is by their own standard of what a lie is, not what a mortal's concept of a lie, is.. There are many shades to the truth, and the Fae are expert and using all of them. Especially with Mab who can twist things to the point where no, she isn't knowingly lying, but nor is she telling the whole truth!
Mab can't make Thomas pure human. According to JB, yes, she could tear the parasite right out of him, but that wouldn't leave anything recognizable behind. She can't surgically, neatly remove the parasite and just leave the man.
Nor if the image Harry saw of Thomas in the soul gaze without the Hunger Demon real, would she want that frail human as her Knight. I think not. However unless there is a way to shut off the Hunger Demon, which Margaret may have learned that secret from Lea or Mab, the Demon would clash with the Winter Knight mantle.. In fact the Demon and the Mantle working together would make quite a monster in my opinion. So thank you for making my point, Mab might not have been lying to Harry about that, but at the same time she has no intention of carrying out her threat of making Thomas her Knight.
That is a damned good question. I've wondered it myself. Is Molly Sidhe now? How much free will does her mantle leave her? We already know she can use cell phones now, but we lack data to determine much else.
Another question that follows whether or not the technobane can be gotten around, if the wizard knows how. Listen's to Wind, keeps current medically, he has attended medical school, it's a given that that means he would be around state of the art medical electronic equipment, that he cannot have blow up any time he enters a hospital or laboratory. Actually there are few things these days in our everyday life that doesn't contain computer chips of some kind. Given what the average cell phone has become these days, Harry walking down the street should make more pants and purses blow up than when the Israelis did it to the terrorists. Some things sound cool, but in reality don't make a whole lot of sense.. Like I could never get beyond Harry taking cold showers during the height of winter in Chicago because he couldn't have a water heater!