Hey Convergence,
I think you're ok. All looks well to me, though there's more experienced people who might have other ideas.
Normally I'd say you need some fresh air exchange, but since you sterilized the soil you probably won't have any issues with mold.
As long as the soil looks moist and you're seeing condensation, you probably don't need to water. If you keep them sealed, that most likely will be post germination.
If the soil looks dry, misting from above is probably best. Contamination is not usually a big deal with cacti seeds, but if you do open them up and expose them, you'll probably need to start opening daily for fresh air, which combats mold/mildew, the main nemesis of cacti seeds/seedlings.
Best of luck. You may begin to see the first signs of babies in there over the next handful of days.