You seem to be doing everything right, so don’t worry too much, it’s very early days for you.
Maybe a good thing to go back on the Metformin if you can tolerate it as although it doesn’t do much work on actual reducing blood sugar it’s roll is to reduce liver dumps or dawn phenomenon (which happens anytime not just in the morning) this could be what’s happening to you with you seeing the slight rise in numbers. I notice a rise in numbers if I don’t take my metformin for a few days (if I get a ducky tummy or something)
The other thing could be that you are sickening for something such as a cold, or a low level infection, you are right that it could be the sleep, even after a few days. Lots of things play a part in our blood sugar levels, it could be hormones- mine went a bit crazy in the beginning of my menopause.
Keep doing what you are doing and you do have a little bit of room to drop carbs further if you wish to. I doubt very much it’s anything to do with calories- calories have no bearing on blood sugar whatsoever