Personally, I've always interpreted Jack's "Won't you?" answer in the epilogue not as Jack being flippant about taking over Christmas, but rather that despite how much pain he caused and went through, everything he found by doing so (his renewed vigor for his own holiday, his friendship with Santa, and ESPECIALLY finding how much Sally means to him and vise versa) made it all worth it and he wouldn't trade all that just to avoid the trouble.
I complete agree with you, anon! That’s actually why I love the Epilogue so much. It was, after all, Santa who came all the way down to Halloween Town JUST to ask him that question. He’s been thinking about the Christmas debacle ever since it happened and, despite it all, claims that he’s still fond of Jack. Enough to where he’d even pay him a visit. He also says that his smile was a lot like the “old pumpkin king he knew” - which is a point to Santa liking how upbeat he is, especially about the Christmas failure.
To me, the question wasn’t at all asking if he would try and take over Christmas again - but to relive exactly what you said, anon. Finding his purpose through all of it, and reflecting on what came OUT of it. Sally, his children, the holidays coming together – they’re all because of what happened. And if asked to take that risk all over again knowing how it’ll turn out, Jack would gladly do it for every reason you said.