like you i do not like a full rubber fuel line,
I would replace the fuel line with copper or steel fuel line, but still leave a space for a metal inline fuel filter.
dirty fuel will ruin your day in these old tractors, the tanks are full of junk, the transfer tanks can become contaminated. Buy the best metal fuel filter you can, it must be a free flow filter.
i have never had problems with my pto (1957 model TO35) but i would not think 1/2" play can be doing anything inside the differential any good. I would get that fixed soon.
change the oil in the lift, use 90 weight mineral oil or motor oil.
I still use the 90 weight mineral oil as called for in the manual, but the lift is a little slow on a cold morning.
check the radiator, it must be clean inside and outside, thermostat, cooling system in general, these old tractors cannot withstand getting hot!!!!!!!!!!!!
one other item to check: crawl under the tractor and look up, around the gearshift area,
there should be a upside down cotter key stuck in a drain hole: the legs of the cotter key will be sticking down and spread out. The key is to catch on grass and turn as you drive around the fields.
This action keeps the drain hole open. most of these old tractors will seap a bit of trans/hyd oil and this drain hole keeps the oil from building up in your trans case and ruining your clutch.
ask me how i know this can happen, and i had a cotter key in place but it was stuck with mud (i got the little tractor stuck so bad all you could see was the upright exhaust pipe, I did not check the drain hole after i got the tractor unstuck. clutches are expensive.
good luck with your tractor, show us some pictures of your tractor.