Your temps are bit on the high side. Try an extruder temp of 230 and lower the bed temp to about 100 (or less even). The glass point of ABS is 105 so you don't want to go over that. Lowering your speed is good too, especially for the first layer and definitely if you have small holes.

Other things I would throw in as a matter of diligence are 1) calibrating your extruder and 2) definitely keep you printer completely enclosed when printing ABS.