For the tail rubbing, normally there is an underlying issue that is causing them to itch. Is his sheath clean? Flies bothering him? Although if it is in recovery stage, most likely the problem is solved. Some people use stuff called MTG (Mane and Tail Grower), however it apparently smells greasy and can cause sunburn if horse is left in the sun too long. Another option is coconut oil. Massage it into the base of the mane, since hair grows from the base, not the end.
For the thick mane, you can thin it by pulling it... Although I like thick manes. To make it lay on one side, you could try braiding it and while braiding pulling down on the braid, which will train it to the one side. I believe you always want the mane on the right side of the neck. Hope I helped!
Intermediate Rider~Learning Equitation and English Pleasure~Interested in Eventing
A horse will tell you everything you need to know about him, if you listen.