The problem with NSAIDs is their effect on the immune response to the virus - they drastically reduce it. Paracetamol and microdose aspirin are ok, pain-relief or anti-inflammatory doses of aspirin/NSAIDs seem to be very dangerous right now. Use dihydrocodeine or similar if you really need it. (No idea about gabapentin or amitryptiline).

I haven't seen any research on fhe effects of fever reduction. My take on it is that fever is an anti-viral response, so you want to just let it happen unless it gets dangerously high - and with COVID-19 it rarely seems to get that bad.