NGL I think whatever you’re trying to do is either a limitation of the Roblox install or something else that isn’t specifically an OS X issue. The file permission stuff sounds weird and I’d reevaluate what you’re trying to do and if the approach is correct, especially if you’re going to have to turn off operating system security features to get it to work.

Let’s Encrypt supports DNS verification, if you have access to update the zone file. It makes automation harder, but there are scripts to do the DNS update for the verification.

As others have said, using dd will be a bit for bit copy of the drive, regardless of the filesystem. If you were only using 10GB, and the rest of the drive was “empty”, the output of dd will still be a 256GB file. You could compress this file with gzip if storage is a concern.

With regard to your plan with Windows, there is a hardware check that OS will perform and if the hardware drifts too much, the OS will not be activated anymore and will need a new license. I’m not familiar with recent versions of Windows, but if you have a Pro version of the OS, it might not work on new hardware.