AFAIK you have have TOFI without evidence on the pancreas / liver, and the only definitive diagnosis is from MRI or CT scans. And I think you have been unlucky to receive such poor support.
I think the advice to eat smaller portions might well be pragmatic - switching to (usually) no carbohydrates at my evening meal has been an 'interesting' journey. You might also be someone who is more sensitive to the carbs you eat than some of us are. I've effectively cut out rice, cous cous, pasta & potatoes.
It's not cheap in the long term, but you might find a few weeks of Continuous Glucose Monitoring helpful to find out what carbs affect you the most. There's information about them here:
Continuous glucose monitors, also called CGMs, let people with diabetes check their sugar levels without having to prick their fingers.
www.diabetes.org.uk
Libre has a 14 day free trial, you need a suitable Android or iPhone:
www.freestyle.abbott