I personally have never overclocked laptop hardware b4, only PC hardware. I have always been a bit worried about overclocking laptops due to heat build up, laptops cannot get rid of heat as well as a desktop, so overheating is always a worry.
With regards to your overclock, I'm sure you can go higher but be very watchfull of your system temps. I use NTune to overclock NVidia GPU's (Dekstop), what are you using? Not sure how much further you can push that card but make sure everytime you overclock, test for stability. I use Furmark or a heavy graphic game for a couple of hours. I would suggest carrying on overclocking, keep testing every 15MHz and watch your temps.