My answer would be the same. Thanks.
For number 1, you might want to attempt mixed grip pull ups to try,
and then alternate your grip every set.
For number 2, no such digits. Your strength might actually vary
too, depending on the condition of the body at the particular point
of time. When you exercise, a better gauge would be by
intensity.
For number 3, you might want to see a doctor or a skin
specialist.
