Wow. Was that high of 360 on your digital thermo? If so, what did the PG read?
Try putting a small handful of pellets right on top of the ignitor. Then, on the same settings 30/100, with the hood left OPEN, you should be able to produce a rip-roaring fire on the grill side in 25 minutes or less from a cold start. If you can't do this, you're not feeding enough pellets and that's your problem.
Bill is right about the LHT. I never set mine below 30, and rarely above. Settings lower than 30 always result in large temp swings for me.
Finally, have you tried a different thermometer and verified that your digital one is working correctly?