The mass of air in a tire doesn't really add to the mass of the bike though... the air particles don't just sit at the bottom pressing against the lower surface due to gravity.
I didn't like the freerunning one... took away the rawness to make it into a silly cinematic scene. Leave that to the Bond films I say! Thought the flatland one was a bit weird too as it removed the smooth, flowing nature of the riding it seemed.
Are you sure the BB axle isn't bent? Is it wobbly as in physical play/movement possible by wobbling it by hand or just off axis movement when you rotate the cranks?
Not if you're running the freewheel on the back you don't .
A 22T chainring at the front is equivalent to standard 18:15 gearing which is used by pretty much everyone who rides 'proper' trials on stock. Stick with it and you'll get used to it.
One thing to note which is most likely unrelated to the problems you're experiencing is that it doesn't look like the spring is seated properly on the pulley bolt that it's supposed to hook onto.