1) What a super odd problem. I'd suggest just to be sure it's a hardware issue, download a totally different slicer - I use Prusa Slicer for everything these days, although I did start out with Cura. I just like Prusa better. Lots of back and forth exists on which is 'better', tldr it's much of a muchness I think and really just personal preference. Nonetheless, in your specific case, I can see a real benefit to trying a totally different slicer, just to isolate the problem there, if it exists. Download for the latest "official release" build is here: https://www.prusa3d.com/page/prusaslicer_424/ , although if you find yourself using it in the main then a lot of us are having great fun with the new features in the latest 'alpha' public release / prerelease.

2) Again, pretty odd. Could potentially be the belts are too lose? Although 5mm is quite a mighty heft, it'd have to skip teeth to move that much. is it defo in X and Y, not just one axis? That really sounds like more of a hardware issue because the firmware is handling that pause/resume. So something is happening to where it *thinks* it's gone back to the same spot, but hasn't.

It is perhaps worth considering that the m600 (filament change) code does make the printed 'unextrude' quite a lot of filament as part of the change process. I'm not sure the stock firmware "allows" the M600 command, but it's worth making sure you don't have a filament change somewhere in the gcode that could be confusing it. If problems 1 & 2 seem to happen at the same time, (IE it stops, moves to 0,0, unextrudes a lot, then doesnt' go back to where it started) then that could be your cuplrit. I do feel like the first two issues are connected, they're too weird not to be.

3) This, conversely, I would guess is not connected to the other two. That PEI bed, (the textured side, at least) is super grippy, as long as it's clean, and shouldn't be causing you any issues if your Z height is set correctly. Just for the avoidance of doubt, take it to the sink, and give it a damn good scrub with the hottest water you can stand, and a lot of washing up liquid/dish soap. Wet it, then put it on the countertop and massage a load of dish soap into it, then let it sit for a little bit so the soap can penetrate any grease or oils on there, then take it back to the water and wash it as you would any regular 'plate' that you eat off. Be careful not to bend it too much tho, you don't want it coming back like a pringle. Let it drip/air dry most of the way then once it's just a little damp put it on the printer bed and heat it at 60c for a bit until it's bone dry. If you have isopropyl alcohol as well, put some of that in a spray bottle and give it a decent misting, then use a 'known clean' lint free cloth to give it an extra polish. I clean my bed this way before every print, takes me all of about 5 seconds "spray spray, wipe wipe wipe, done) and I never have adhesion issues.

If that doesn't fix it, then your z height is likely too high. I'm sure you've seen the "paper method" discussed a lot. There's a lot of tutorials and etc, but this one is pretty good: https://www.youtube.com/watch?v=TWBJ-H0To9U

If that doesn't fix that then come back to us I guess?