This is frustrating. Last time I checked, the gate agents dont do weight and balance. To the guy who got bumped, put in a word with your union jumpseat committee.
As for being PIC on the ground at QX, I disagree with what snackysmores says. If the CA puts a stop to boarding, you may get asked why at a later date but thats it.
I start my APU at my leisure (every leg), and have never heard a peep from anyone.
If I want fuel, the aircraft doesnt move till i get it... sometimes being a CA requires you to not let people railroad you bro.