120 - 130 is fine, when hes small best to go with 120, when hes full grown you want a spot that is 150, mine i use the morter style, cinder block, the ones wih holes in them, so ontop its 120 and inside its around 105 or so, its best to give him a few hotspots so he can pick what heat he wants to be at, i recomend building yourself a bigger cage sooner than later. eventually you need 8'x4'x4' so may as well build it now and use it while he grows

he looks great by the way, about the same size as mine. i dought he has ri if your temps are on, most likely just digging and had stuff in them :P