Disk Caliper wont go back on

I usually tighten the spindle nut snug while turning the rotor to seat the wheel bearings. Once seated, I back off the nut then make it hand tight. Otherwise the bearings will be too loose in the races, will destroy themselves. you will eventually feel it with a clunking and loose feeling in the front end.

As far as the calipers go, of course the left one will feel tight if you pushed the pistons back on the right one to put it back on. You moved the fluid back to the left wheel by compressing the pistons on the right side making them compress the left brake.

The proper way to compress front brake caliper pistons is to take the lid off the master cylinder. Hydraulic fluid will push upward to path of least resistance. This is why when your brake fluid is low, check your pad wear first. As the pads wear and pistons move out to maintain rotor contact, the reservoir fluid gets low. I dont add fluid when it gets low. Because when you push the pads back, the reservoir will then overflow.

Maybe your pads on the passenger side arent pushed back far enough giving you enough room to move the caliper around.