Editing, you call it? You mean changing something you've already written? What's the purpose? Nah, it'll never catch on. At best it'll just be a fad. Better to invest in crypto currencies.

Sewing machine oil and gun oil are silicone based oils and will evaporate cleanly. Petroleum based oils, like 3-n-1 oil, will also eventually evaporate but will leave a gummy residue that you don't want in fine machinery. (WD-40 is also petroleum based but I don't think that stuff is even classed as an "oil")

I like standards. I always feel like portables are giving up something for the "portability" factor. Image quality and keyboard feel are the biggest factors in the typewiter experience, in my opinion. And the standard typer doesn't cut any corners in giving the user those qualities.

I have a 1940 Underwood Master. I would use the Ames repair manual for repairs. The download link can be found several places so you can get it off the internet. the innards of the Master is practically the same as the Underwood No. 5 (why mess with success!)

I have a couple of typewriters that take a loooong time to switch ribbon directions. Consequently, there is a spot at the each end of the ribbon where the slugs keep hitting the same spot over and over while the typewriter mechanism does its direction-switching thing. I wonder if you are typing single spaced, in which case a ribbon length might only last for 1-1/2 to 2 pages. (Or maybe you have a shorter ribbon than most.) It's just a possibility that you are reaching the end of your ribbon and there is a "dry" spot. Best fix for that is to recognize when you are close to the end and manually switch ribbon directions.