Hey all was wondering if anyone could shed any light onto a few of these problems? (Astra SXI 1.6 16v z16xe)

1st of all i oil spilling at the corners of the cam cover, i changed cam cover gasket and seemed to get worse! Also Arent the screws meant to have o-rings on the inside of the cam cover? when i took mine off there wasnt any o-rings, and i didnt get any with my gasket. It only does it while driving and under pressure.

2nd i get dodgy idleing, it will be fine 1 inute then the next drops to almost stalling then rev right up then repeats (this is while waiting at a junction for example) ill set off and come to the next junction and be fine, seems very random

3rd if i turn the A/C on and am idle the revs also jump up and down

Finally does anyone know what sort of mileage you get from this engine just driving normally? i do a fair few 10-15 min trips and i get about 250-280ish which i think it pretty low since i got more from my GSi.

Can take some pictures of whats wrong if i havnt explained it very well