At the beginning, before you have a good sense of where a dose will take him, the recommendation is not to shoot under 200.
I'm hoping some of the more experienced folks return soon to offer guidance, but here's what I know:
1) with the insulin on board and such low numbers, you need to monitor very closely until the numbers start going up.
2) hold off on feeding a ton of food right now, you may need to keep feeding to keep the numbers up
3) if you do give food, with a number like 26 I think you should be giving high-carb food-- gravy from the Fancy Feast gravy lovers is a favorite, but another option is to put a bit of honey or Karo syrup on the usual low-carb food.
4) in a pinch, a bit of honey/Karo on the gums (it will absorb in, he doesn't have to swallow) will quickly (though briefly) bring numbers up.
More in a bit.