Hello, JC, welcome to the forum.
It looks like the gentlemen here have addressed all of your concerns except possibly this one about kefir, “Kefir was recommended on this site a few times. I was wondering if the lactose was a bad idea.”
The longer kefir is fermented, the less sugar or lactate will remain in the final product. The fermentation will remove all or at least enough of the sugar to prevent problems.
Kefir can be the most beneficial food/supplement/probiotic that you take during your treatment.