I believe on the Azodin regs, screwing it in will lower the pressure.
I'm not quite sure why it was leaking, but it sounds like its fixed. The orings on the valve could have been moved from too much pressure, causing a squeaking noise close to around where the bolt sits or the valve could have just been open a little bit.
If you want to increase FPS, just use the velocity adjuster on the back of the marker. Screw it in a bit until you get closer to where you want it. You MIGHT not get where you want it, but you could get close. Not to say that 280 is slow however.