After the week of bouncing between -50 and 200+ I followed Matt's advice and got up every couple of hours throughout the night to see what was happening to the old blood glucose. I'd expected that it was dropping and then bouncing back high but that wasn't the case. It stayed around 200 the whole time. I definitely didn't want to fiddle with the basal rates now.
Then on the fourth night I tested my blood before bed and it registered 132. I decided I'd had enough mid-sleep finger pricking to last a while and I was just going to forget about it. Number on awakening? 106! And it's been fine ever since.
I don't know what was going on for those 7-10 days, maybe I was stressed, maybe I'd exercised harder than usual, maybe... who knows? It's one of the more difficult aspects of diabetes that there are no absolutes, no norms and often no answers. We struggle for perfection but sometimes we have to settle for just muddling through.