As I said, booting it with a fabric patch on the inside is the right way. I have seen boots applied to the outside, but it's a very short term solution, though it might last a bit longer than doing nothing.

The beast answer is situational. Years ago, on a tour I fixed a similar problem with cloth adhesive tape wrapped around the tire and rim. It was a quick fix, and meant the loss of the brake, but I had a train to catch, and this made it possible.

Normally, I don't consider blowouts or any tire failure especially dangerous, so I'd endorse a makeshift repair. But if the area where your husband is is really as bad as you describe, the risk of being stranded rules out an unreliable repair, unless there's absolutely no other choice.

There's also the skill question, makeshift repairs other than the tape require some skill in execution. If your husband had to email you the photos to get an opinion, I doubt we could explain to him how to do something he could trust.

It's really about options and choices, and not knowing the details of the situation, I can't say what the smartest course would be.