Is that mold?

Correct.........mineral/salt residue.......not mold.........no need to do anything.

Nope just keep going. The white on the fabric pot is most likely mineral build up from the fabric pot getting extra moist and then drying out.

I'd say oxidized nute residue, but hard to tell

salts build up

Looks like some small roots to me. Probably the wet pot was softer and the roots had it easier to find their way through. Just by judging the picture I would say "everything fine".