To stop a bolus I press Act then Suspend then Resume
To prime an air bubble out, disconnect the infusion set from your body (obviously) then go to Act, Prime, Fixed Prime and put in the number of units you want to push through.
I’ve never had more than the tiniest of bubbles (like you could barely see them) but I know others have problems. Are you sure it was an air bubble? I find the tubing quite often gets marks on it that look like air bubbles, but don’t actually move and are in fact just where I’ve compressed the tubing by bending it and it’s bounced back but looks a different colour.