since I was an EHK baby 30-ish years ago things have changed but I will answer your questions in case something helps.

1. does anything you eat have ANY effect on whether you get blisters or not?
No, not one bit in my experience

2. do you have finger/toe prints? (especially for those with palmar/plantar EHK)
I don't have palmar/plantar and I do have prints - no life of crime for me!

3. is an infection really that noticeable or should I be checking temperature regularly?
I never get a temperature with an infection as it is very localized to the area of the blisters. If I have a temperature due to the flu I get itchy and then I peel a couple of weeks later.

4. which hurts most, the blisters or cracked skin, like behind the knees?
There are different types of blisters. The "deep" ones hurt more and have more "burning pressure" than cracks. Cracks are painful in an annoying, stinging kind of way. Are you sure the crack behind Ivy's knee isn't just a crevasse in the skin to allow mobility? Is it red at the bottom of the crack?

5. does your EHK baby sleep in positions not recommended by the pediatricians? (side, stomach, etc.)
I don't know how I slept as a baby but everything has changed anyways. I sleep on my side all the time now.
Sarah & Son
"Today is the Tomorrow that you worried about Yesterday, and all is well"