The numbers you quote are very high. Especially the 30.2. It may well be that going into hospital for IV insulin until his BG stabilises is the best way to go. I know that insulin dependant T2s who are very poorly controlled on diagnosis often go into hospital to stabilise before they start their insulin regime.
Has anyone tested for ketones? The numbers are high enough to carry the risk of Diabetic ketoacidosis (DKA) which can be very serious if not caught in time.
Anywhere above 15 is getting into a risky area.
I note that the T1s haven't mentioned this yet, but I should keep a close eye on him for any unusual symptoms and be prepared to ring 111 or even head for A&E if in doubt.
https://www.nhs.uk/conditions/diabetic-ketoacidosis/#when-to-get-medical-help has some information but seems to assume that you can test for ketones. As far as I know you are usually only set up to do this if you are insulin dependant. Does he have Ketostix or a blood ketone meter?
@Jaylee for a T1 view on this.
I would also look at having his care taken over by the diabetic clinic at the hospital as the conditiopns you describe should not be allowed to happen.