I have the same drivetrain you have. All SRAM eagle chains will work. XX1 is the top of the line and should give you no problem.

Was the old chain an SX or GX, like I said before, those wear out extremely fast and can ruin your cassette. It's a well known problem.

The quick link to attach the regular is a flat top. Did you connect it facing the right way? Flats to the outside of your circle.

All Eagle derailleurs look bent inward. It's how they are. If your hanger is straight, don't worry about what the derailleur looks like.

The upper pulley on an eagle derailleur is narrow wide and well as the chainring. Due to its size, it's actually difficult to get it wrong. Double check though.

Make sure you've threaded the chain correctly into the der. This is more of a road bike problem but check anyway.

I'm going with my original post on this, that the older worse quality chain wore out your drivetrain. Those chains really should come with a black box warning.