Since I don't know the temperatures around your parts, I would be looking at the R values. But, 1 1/2 board does a decent job.

I do r13, so mine was 55.

A serrated knife cuts it well. Or, Home Depot has some pink board with perforated lines to allow for easy sections.

Insulation is hard to do nowadays less than a 100. Might get foam board and cut it down.

If you seal the bays with plastic, you could do blow in insulation.

I have limited experience, but depending on the fixture there can be (note can be) a smaller fuse inside the motor that could interrupt the flow. Might find a part number and see if there's a manual running around the internet.

Sounds like the motor has gone bad, at least. Probably needs to be replaced, depending on the age of the house and fixture.

I've had decent luck with the command strips by 3m. I think they make a roll of it.