Why is it either no cardio or cardio every day?
You could just run the days you don't lift.
Lots of people can get below 10% w/o cardio, I don't know anything about diabetes or how this would complicate things.
If progress is slowing, try cutting your calories by a hundred or so and see if that works.
Running a few miles would also effectively create that caloric deficit.
I want to say elevated heart rate due to weightlifting is slightly different than true energy systems work, but I wouldn't swear to that or be able to explain why.