Is he using a pump or shots?  Our son is very hard to regulate and was put on a pump when still 2 years old (diagnosed at 25 months, on pump just before 3rd birthday).  We had fits with the long acting insulins and the pumps eliminate that.  We have changed pumps to get to one that can administer doses as small as 0.025 units.  That has helped us do better at stabilizing the BG.  However, just when you think you have something figured out, things change.  That is just the nature of the beast.  Just keep working at it and keep as good an attitude as possible.