The thing you popped off was the outer coating of the seed... The less we mess with our plants the better.
The best thing you can do is keep it at 50-60% RH with that Dome, + Get a good light. And keep the temps below 95, above 70...
You cant use that dome forever, You are going to need ventilation. Plants like to exchange the used up Co2 in area, and need the leaves to be stimulated (a fan blowing on them)
When the plants get mature enough, They are going to need darkness for 12 hours.and low humidity.
Feel free to ask anything! no question is a dumb question