The mobile version's background moves, but i don't want it to.

This happens on IOS. I'm told that Safari doesn't support fixed backgrounds.

Is there a workaround? Setting an actual picture as sticky moves it above the content.

Is there a way to make it sticky but still be on the bottom layer

Doesn't 'Stick at top' work Branden?

Try:
Utilities > Web Animation > Reveal/Scroll
Select Scroll and choose Parallax from the drop down and leave the speed at 0.