How to clean glue or adhesive from film?

Perchloroethylene (Perc, Tetrachloroethylene) available from Amazon.

Wet a well-washed "T" shirt with this and swab both sides. This is the stuff of Cine film cleaner.

I have encountered this same problem, and I can sympathize.

Pec-12 does remove the adhesive

If the glue were water soluble, Pec-12 would have no effect, so this tells you that it is not water soluble and there's no point soaking your film in distilled water (unless you want to give it a good cleaning).

The pad gets stuck in the film indents; have to unfold/refold the pad to get a fresh clean surface; resoak with Pec-12.

Since you only want to clean the edges, try a smaller applicator. Cue tips with Pec-12 are easier to control than those large pads. It won't solve the tedium, but it will minimize accidentally hitting the image emulsion.

This sometimes leaves streaks on the film

Using too much Pec-12 will leave a white haze, but if you let the excess evaporate, you can go over the area lightly with a small amount of Pec-12 and the haze should disappear.

Since the adhesive I want to remove is across the film's sprocket holes, I'm concerned that if I cover the sprocket holes the scanner won't be able to feed in the film.

You are right to be concerned about the sprocket holes if you are using a negative scanner, like the Nikon 5000, which needs them to feed the film strip into the scanner. Getting rid of the glue is the only solution, and I don't know of any quick and easy way to it. Removing the adhesive without damaging the emulsion is a tricky proposition, and patience combined with a product safe for emulsions is key.

Try putting the film (with the paper still attached) in the freezer for a few hours. Carefully remove the paper and, most of the time, the adhesive will stick to the paper and not the negatives. If this doesn’t work, chemical cleaning methods would be plan B.