Could it be that the unicycle saddle is not ideal for your arsular dimensions for long rides? Most touring cyclists try a few saddles before settling on one they like. If there are other Unicycle saddle shapes, try one of those. I am not familiar with the unicycle aftermarket for saddles though - if there are few options then you might have to try something else.
Also, creams and balms are often used, even for very high-mileage tourists.