The dark bag part is right but the respooling itself doesn't actually need total darkness, most films are fine with a little light as long as you're not pointing a lamp at them. What really matters is doing it by feel and keeping the spool tight so the film doesn't telescope or get scratched. Your neighbor probably meant that part, the habit of trusting your hands instead of your eyes. Either way it's one of those things that clicks once and you never go back.

Long arcing on the root is not some big secret problem that needs a deep fix. Half inch off the plate is a lot, yeah, but that is just basic arc length. Every guy learning sticks deals with it. Not saying your old timer was wrong, he gave you a solid tip. Just seems like you are making it out to be some huge embarrassing thing when it is really just normal stuff that happens when you get in your own head. Three tries on a cert test is nothing, plenty of good welders took more than that. Tight arc is rule one and sometimes you just need somebody to say it out loud.