When you stimulate, wrap him up in fleece to keep him warm and feeling secure. I find the best stimulation technique for fussy squirrels is simply a wet fingertip (warm water).
Looks like you are reverting back to Esbilac without the Fox Valley... I'd stick with Esbilac until after his eyes open.
He is not clicking when he breaths is he? Hold him to your ear like a phone and listen for a consistent click sound.
In reading through this thread I do not get a good sense of how often you are giving him formula and / or fluids, so clarifying that would be helpful. Very helpful.