As many have said, your preflop raise is way to small. You are playing a freeroll with deep stacks, and if anything this is a situation, where you want to size up with your best hands including JJ. You can raise to 4-5BB here and still get someone to call, which will print a ton more value and lead to easier postflop decisions than just mini-raising and getting a cascade of callers.
I also think, your flop C-bet is to small, and as for his jam, folding is certainly not bad, but since its a freeroll, and you had seen him do this before, I might actually have called this off. You are only in really bad shape, if he has exactly JT, and you block that hand down to only half its normal combos. So why not just get it in and gamble against him? If you lose, at least you are done with the thing and can spend your time on something more important than a freeroll.
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