We went through the adoption process about 17 years ago, neither of us were diabetic then (i am T2 now) but my husband had epilepsy, well controlled. Our panel doctor had extra questions too and it we were approved without problems, it's just they like as much info as possible.
I doubt very much if T1 is a barrier to adoption as they would have told you that right at the beginning of the process - that is if you disclosed it then.
It is so much better these days, when we got our son a year after approval it was a rule that the main caregiver give up work completely without any maternity pay or partners rights to paternity leave, today you get the same rights as a couple having their own child.
I wish you all the luck in getting your family, the road to adoption can be difficult and painful and sometimes heart breaking when you are up against other couples for the same child, but so so worth it and I have never regretted a minute of it although our son turned out to have special needs he is our pride and joy and has grown into a fine young man, he hit 18 last week and it was a great milestone for all of us
The very best of luck to you both