Sarah Jane you have a very big heart. Thank you so much for helping this little one.
A couple of things.
1. Make sure the heating pad is outside of the tote, under only half of it, so baby can move to a warmer or cooler spot as needed. Inside the tote can become dangerously warm. I have seen baby animals die that way.
2. Hold off on feeding solid foods at this point, until you can get the proper stuff. Crackers and especially nuts are inappropriate at this stage.
3. The correct milk is going to provide baby everything she needs until you add a squirrel block (food). She should not be on a kitten replacement formula. There a couple of options, but if the quickest thing you can buy locally is Puppy Esbilac formula--
this exact powdered formula. *buy a kitchen gram scale (walmart) because you'll need a weight to determine how much to feed from now on.
Also, you are off to a great start, it sounds like you did some reading and know that you have to feed with syringe and not a bottle, must pee and poo them at every feeding time and to keep baby warm. I think you just have to smooth out the details now.
Check out this site, click through all six pages and read everything. Come back with any questions you have. We're here to help!
http://www.henryspets.com/baby-squirrel-care/