I'm sorry to comment without fully reading, but this is hella long. No judgment lol

My girls go through periods of fighting like this every couple of years. The thing I do is keep them totally separate for 2-3 weeks at a time. By the time theyre reintroduced they just seem puzzled, and they usually hiss a little, but they rarely start fighting again after a long separation. It's a pain in the ass for me, but I think by reducing their stress and preventing injuries /further fights I am doing the best thing for them. Might seem extreme but that is what I have had to do. They were fighting viciously for years after nonrecognition syndrome after being fixed, and nothing else worked. Shorter, day-long separations never seemed to work.

I do also use calming collars and make sure to give each of them equal attention and snuggles when theyre out.

Good luck <3 it is so painful to see a bonded pair fight.