I just reread your post and you are talking about turning an auto flower into a mother plant. I don't think this will work.
Starting from only one seed is really putting all your eggs in one basket. Lots of things can go wrong. As for a plant turning hermie because it was exposed to stray light by running down the hall, I don't think that is a factor. I think you can turn on the light for a minute or so during the dark flowering cycle and the plant won't have time to react, let alone turn into a hermie because of this. I think you need to get some stuff that turns one branch into a male and get your pollen that way.
I recently had a Nirvana Blackjack that was really bushy. As soon as I identified that it was female, I chopped off one of the six inch offshoots. I put this in water overnight, just to make sure it was hydrated. Next day I put it in a beer cup with holes in the bottom. I filled it with soil, burying a good three inches of the stem, trimming off any leaves that would be beneath the soil level. Next I watered the soil until it was coming out the drain holes. It sat there for five days looking perfectly happy, but not really growing. Then it grew an inch in the next three days, at which point I topped it. Next week, when the soil drys out again, I'm going to transplant it into a bigger pot. This will be my mother plant. I've already proved that it was easy to clone because I put directly in soil with no root treatment at all. The key is you need nice long shoots of six to nine inches. Put lots of stem under the soil.