Do you test your blood glucose before during and after running?
If not ... why not? It would be the best indicator of what would work best for you and your type 2 Diabetes whilst partaking of the sport.
Definitely would recommend getting your running gait analysed and the right running shoes for you selected - assuming you haven't already.
Your running journey looks really good to me - having built up to doing a half marathon I would have hoped you'd have a really good understanding of how your running has impacted your type 2 Diabetes.
Diet will become a critical element if you wish to run longer distances or even improve your performance - food is fuel!