If you're going to put anything on the threads some of the tire patch glue is what I'd use. Just rub it in so the threads are sealed against water. Shouldn't take much.

Keep in mind that the tire IS living a shorter life now. It'll be fine for a few months most likely. But just in case inspect it every hour or so of riding to see how it's fairing. It may well be fine for months to come. Or perhaps part of the damaged area will begin to bulge apart in a few days or weeks. In any event you'll want to keep a close eye on it from now to when it's finally replaced.