High Temp CPU

Either the pump is not running, there is an airlock or the cold plate is not seating fully due to interference with something on the motherboard. If you are absolutely positive that you've used the correct backing plate and stand offs for the type of socket your CPU uses (Most kits come with multiple backing plates and stand offs) then there is either a pump or airlock issue or there is something not allowing the base of the water block to seat correctly.

Your temps are not normal and are far too high. Where is your pump plugged into? You want it plugged into something that allows it to run full speed at all times. You do not want it's rotational values to vary based on temperature. For fans, that's fine. For the pump, not so much.

Go into the bios and check the RPMs being reported for whichever header you have the pump attached to. Pretty sure something is not connected correctly or there is interference somewhere but it's equally possible that it simply has a bad pump. You can at least tell if the pump is running by putting a finger on the top of it to see if you can feel the vibration of the running pump.

Might be a good idea to strip it back down, look for any interference points around the CPU socket on your board that might not allow it to fully seat, look for any marks on the bottom of the hardware that might indicate it HAS been sitting on something and watch the following video to make absolutely certain you are connecting everything exactly the way it is supposed to be connected.

https://www.youtube.com/watch?v=xKGbu6ywCW8

It's also possible, but unlikely, that your fan configuration is wrong. Where do you have fans located and which of them are oriented for intake and which for exhaust. I doubt this is the problem, but it could be a contributor. I'm constantly seeing people here with two front intake fans, a top mounted radiator in intake configuration and only a single rear exhaust. That creates so much internal air pressure that the fan on the radiator are barely able to pass any air through it in order to function correctly. Again, that would only contribute, no cause the problem in full.

Either the pump is not running, there is an airlock or the cold plate is not seating fully due to interference with something on the motherboard. If you are absolutely positive that you've used the correct backing plate and stand offs for the type of socket your CPU uses (Most kits come with multiple backing plates and stand offs) then there is either a pump or airlock issue or there is something not allowing the base of the water block to seat correctly.

Your temps are not normal and are far too high. Where is your pump plugged into? You want it plugged into something that allows it to run full speed at all times. You do not want it's rotational values to vary based on temperature. For fans, that's fine. For the pump, not so much.

Go into the bios and check the RPMs being reported for whichever header you have the pump attached to. Pretty sure something is not connected correctly or there is interference somewhere but it's equally possible that it simply has a bad pump. You can at least tell if the pump is running by putting a finger on the top of it to see if you can feel the vibration of the running pump.

Might be a good idea to strip it back down, look for any interference points around the CPU socket on your board that might not allow it to fully seat, look for any marks on the bottom of the hardware that might indicate it HAS been sitting on something and watch the following video to make absolutely certain you are connecting everything exactly the way it is supposed to be connected.

https://www.youtube.com/watch?v=xKGbu6ywCW8

It's also possible, but unlikely, that your fan configuration is wrong. Where do you have fans located and which of them are oriented for intake and which for exhaust. I doubt this is the problem, but it could be a contributor. I'm constantly seeing people here with two front intake fans, a top mounted radiator in intake configuration and only a single rear exhaust. That creates so much internal air pressure that the fan on the radiator are barely able to pass any air through it in order to function correctly. Again, that would only contribute, no cause the problem in full.

If you had actually read my post, you wouldn't have had to go looking for the answer, because that's EXACTLY what I told you to look for.

^^^Yes, IF there is slack, even after you've tightened the backing plate to standoff fasteners fully. If there is not slack, then not 100% necessary. Well, probably doesn't hurt to do it in either case, just to be sure. Might also help to provide some amount of cushion to allow slightly tighter tolerances. Probably good advice. I am definitely not against doing this.

37 and 55 are fine. Normal. 60 and 90 are not. I really think you have multiple problems where you probably mostly solved the mounting issue but are having intermittent pump operation or something.

Too thick washers, placed where?

The whole purpose of the washers is to increase the thickness of the motherboard, so when the backplate is attached to the mounting studs, the mobo/washer combo makes it so the studs actually tighten down to the motherboard surface. More than a few motherboards are relatively thin and what happens is the studs bottom out on the backplate screws leaving the studs loose to the surface. This means there's movement of the studs, never allowing the pump to get fully seated on the cpu. Aio pumps are more effective with higher pressure on the cpu, better thermal transfer.
So no, the washer thickness will not raise temps unless you put the washers on the front of the mobo. They should be on the back, sandwiched between the backplate and the motherboard.