All very true, but also all not without precedent, like James Dresnok. Granted, that was before the days of people going on anti-DPRK propaganda book tours, which is a very real risk like you pointed out. He would definitely be under an immense amount of scrutiny, as he should.

There is a chance, depending on how long he was stationed in SK (I didn't find that detail at first blance) that he may have learned at least some nominal Korean while there. I would wager not a lot, given my experience with US military in my own country, but it's a foundation at least.

I do hope that if he is sincere he can live a full life there. I spent some time there, and while I was not planning to live there longterm there are definitely some opportunities for foreigners. It's honestly probably even more comfortable now than the days of the Korean War deserters, there are a lot more modern amenities that westerners may expect. No iPhones, but most people do have smart phones and access to the Kwangmyon intranet, for example. Is that enough for him? I have no idea.