Timmy, I would recommend trying out this dandruff shampoo (from vitamin shoppe):
I use it every other day and it completely eliminates the dandruff. I have used the tea tree oil shampoo and it is largely ineffective. One thing that did work though, is getting tea tree oil and applying it directly to your scalp; it made the skin feel a bit more happy and reduced the inflamation.
A second idea would be to try acupuncture; they can puncture specific points that will get your body working correctly again (for a few weeks). The only bad part of is its expensive and it doesn’t last long enough; the more frequent you do it the more normalized your body becomes.
I think the gas thing is pretty normal and can last long term. One thing that typically happens with any immune system issues is that your galbladder/digestion gets funky, so the body brews the food internally awhile. Again, acupuncture can significantly help with digestion.
Hopes this helps!