I can understand your worry. Has your partner spoken to their GP about the seizures? (Aswell as his diabetic team) I've used to have seizures from hypos - all at night. For me, I could go to bed with a good blood sugar and still have a seizure. My problem was that the long acting insulin wasn't matching my needs at night and it was impossible to control my blood sugars. I now have a pump and am fine.
My point there is blood sugar can suddenly drop during the night even if you do everything right.However, I'm not sure about the 6.1 you got.
It must be very stressful for your partner and you. If the seizures persist, could you ask for further tests, if only to put your mind at rest?