Just checking that was +4 80. Is that correct?
I would retest in 30 minutes. When you are early in the cycle and the numbers are lower than normal it is a good idea to keep testing until the numbers start to go back up again. If you leave it an hour, it can drop quite a bit, whereas if you test in 30 minutes you can intervene with food or honey to stop it dropping further.
If you find a dropping numbers always test again to check it has not dropped further.
Because you have DKA in the picture, you want to keep him on insulin at the moment. He has dropped below 90 again today but because you took a reduction yesterday we don't recommend back to back reductions. But it might mean you might have to feed some higher carb food. So I would go out in the morning and buy some FF 'gravy lovers' cans.
We always recommend you have some higher carb food available at all times for low numbers.
It's good to see you are testing frequently for ketones.