Unfortunately so much of this is trial and error. It would be impossible to tell you what to do because we are all different.

Maybe you could soak your hands in diluted grapefruit seed extract? That may control it to some degree ( of course it's only symptom control ) :-)

As for the fermented foods that also depends on the person. You will have to try it and see for yourself. I did not do well on Kefir grains, but I am highly dairy intolerant and I also think the natural alcohols also bothered me. It caused my gut a lot of pain. Ouch!

However, I'm improving dramatically by eating raw sauerkraut.

Yeah I wish I could get my fillings out too. The cost is astronomical and that is if you are lucky enough to find a REAL biologic dentist ( not a dentist saying he can remove them...Dangerous! ) And then there is the problem of what to replace them with. I've seen a lot of people on these forums who have had trouble with their replacements. It's a tricky situation that's for sure.

If the black under your fingernails is mold(yeast) you can kill it by rinsing your hands with hydrogen peroxide. You'll have to get it up under the fingernails. HP is a sterilant. It kills both fungi and bacteria. It will bubble and fizz as it sucks the oxygen from the microbes. It will fizz from the cracks in your skin, where microbes have been allowed through your protective layer of skin. After a few minutes rinse your hands off. Then take a big leaf of aloe you can buy at some grocery outlets. Cut off a 1" square. Filet it down the middle of the gel, leaving you two squares with the green peel attached, to hang onto. Rub the allow around on your hands and anywhere else your skin in drying out. You'll have to get it up under the nails somehow. You can use your fingernails to slice the gel to help it flow.
Cracking of the skin is an indication of underhydration. This can be from not drinking enough water or a condition that dehydrates you. Molds, like yeast, suck the moisture out of your body for their own use. That is why you get cotton mouth from drinking alcohol.They require moisture, heat, and biological material to grow. Be sure to drink at least 8 glasses of GOOD water each day to give your body what it needs so it cancombat what the mold takes. You need to engage anti-fungal protocols. This is the first night on this site. I don't know if it is ok to put the name of my web site I am building, on here. After a toxic mold exposure I set out to learn more than 99% of the doctors about how mold effects the human body.
Anything fermented is molded.Alcohol, cheese, etc are all molded products that add mold to the chemistry of your body, upsetting the fungi-bacteria balance. Caffiene drinks like coffee and sodas along with alcohols all dehydrate your body. I hope this will help.