hi! currently FARP territory is 400x400 meters square, but sometimes landing pads placed outside of this area so only way you can use ground support functions is roll around or take off and land closer to the keysite icon on the map. it's common game issue, but I didn't tried to fix it yet.
nose gun has three modes - Pilot's control, Operator's control and stowed position. if Pilot's NOSEGUN CONTROL and ARM MASTER switches are enabled, gun fixed at zero angles - you can use it like boresight weapon with automatic or manual aiming. if NOSEGUN CONTROL is disabled and Operator's ARM MASTER switch (round metal plate on the left handle of Operator's collimator) is enabled, gun can be controlled by this collimator (enter aiming mode with F3 or disable frictional brakes, but it's not good idea). in other cases gun fixed in stowed position and can't be used.