How long have you actually had this snake? What's his setup like, his feeding habits and where in the house is his tank located? Sometimes a change to a quieter location, covering three sides of a glass tank or adding in fakes vinery/coverage can help the more flightly colubrids settle in better. Is he a good, consistent eater so you can assume this isn't a food driven reaction? Does he have hides or deep aspen he can retreat into/under so he feels less exposed and reactive? How about things like loud music, a lot of foot traffic near his home? How do the humans that handle him react when he strikes wildly at them?

Sometimes some small changes can really help our little scaley friends to adjust better. Three or four times a day handling, if he's already stressing over a housing situation is probably adding to his defensive striking so perhaps cutting that back while you reassess his living situation might be in order.