Oh, moving tanks is the best fun...
This is a 30G right? Leave the sand as undisturbed in the tank as you can, cut a piece of plywood slightly larger than the tank footprint to carry it on. That will relieve the stress on the glass.
If you add more sand, you will possibly see a mini cycle, it depends on how well the established bed comes through the move. I wouldn't add 2-3 inches at once though, I'd put it in gradually over a couple of months (that's just me though).
Last time I did a real 'move' I changed out about 50% of the water, temp becomes an issue if you're moving more than a few miles away (both existing water and make up water).
As far as a holding tank, I've kept (hardy) fish in 5 gallon buckets overnight (with heater and powerhead) with no problem.
Get rubbermaid trashcans, they have strong handles
Don't know about the stain.
The only other advice is good friends who work for beer!
(I'm glad someone is getting rid of a damsel)