How is movement calculated when running up walls as a monk?

Picture this circumstance. I am a 5 foot tall level 9 Wood Elf Monk with Mobile. I have 60 feet of speed per turn, via:

  • 35 feet from Wood Elf feature
  • 10 feet from the Mobile feat
  • 15 feet from being a level 9 monk

And can run on walls via the monk’s Unarmored Movement class feature.

I am 15 feet away from a medium sized melee combatant in a 5 foot wide corridor with a 20 foot high ceiling.

Avoiding all attacks of opportunity against me and without using any attacks from me and only the wall movement + speed listed, what is my maximum possible remaining movement to be on the other side of the combatant, out of range, with this setup?

To simplify this, I want to run up the wall, around the guy, without giving him a chance to hit me with his 5 foot range, and still have as much movement possible.

You know, normal Monk things.

My main concern is how the movement starts, and how diagonals work while wall running. Do I spend 5 feet to start “wall running” in the same square I’m in, or do I start by spending 5 feet to be 10 feet in the air? Can I simultaneously move forward while moving up?

I’ve also considered the potential of dropping while on the wall to conserve movement (presumably 10 feet past the combatant), and I want to suggest that for anyone to consider it themselves as a potential part of the answer.

Considering how abstract this question is, there may not be an official answer in 5e, but references to prior editions/Pathfinder on this topic would be valid substitutes.