dddd

Certainly in most cases the bottom bracket bearings can be lubed from the outside, allowing some thick oil to drip in, down along the spindle with the bike laying down on the side.
That should be good for at least a thousand miles or a year of use in decent weather conditions.
***EDIT: I see that 3alarmer beat me to this suggestion! I also use Phil oil, but in cold weather it flows most slowly!***

So I would leave the cotter crank alone for now, it was installed correctly at the factory in almost every case I can think of.

So likely a 1971 or '72 Stella, a nice find.
Likely the Suntour derailer replaced a Campagnolo Valentino derailer, which would be for the (much) better.
Campagnolo's Valentino rear derailers were good in name only, were somewhat of a disgrace to the brand.

Tire pressure should be based proportionally on rider weight.
For my 150lbs I run a 700x23 tire at mid-90's pressure.