There's simply no feasible way to withdraw the funds on lower end puzzles like #66. It will be snatched up by bots. Not maybe, but it's 100% guaranteed. There will be hundreds of withdrawal transactions with varying fees all battling each other. You will simply be left in the dust.

It's a fundamental flaw in this puzzle that was originally aimed to bring the community together and try to solve the puzzle. The puzzle creator did not think much about the puzzle, and this is proof of it.

The only way the original solver will get the funds of puzzle #66 is if they can prove to be in possession of the private keys directly to the puzzle creator. The puzzle creator then withdraws the funds at a 6BTC fee (they can afford it) to your address.