ECID so food might raise his BG a little but if you’re feeding low carb, then you should be fine to feed up until +10. Since Walter has a history of DKA, I would feed him if he’s hungry. Ketones form when there’s high BG, not enough insulin, and not enough calories.
edit: I agree with Wendy too. Usually we try to feed the bulk of their food before nadir so preferably a zero carb food is best after nadir.
I’m sorry you think you did a FS. It might also be an ugly bounce from the nice blues Walter saw last night and this morning.