Nick,

Good luck. I'd instruct. Ask any "jet captain" out there what one of their most memorable jobs was and they'd answer with flight instructing. 300 hours is nothing. You can't even be a day VFR 135 pilot. Don't think you are committed to aviation because you have "paid 40,000" for flight training. Furthermore, I don't know if Gulfstream is even around right now. I think you have the wrong attitude for this industry.