i hear its 81. can the jail exploit still be utilized in TES 5?

I think jail now only gets rid of progress towards the next level of a skill, it doesn't lower the skill itself.

This is true. You lose only progress towards the next level, not actual levels.

There's always the uncapper mod if you really want more levels and perks.

We need an reverse Oghma Infinium or an idiot ball to reduce skill levels,
Object itself should be trivial to make once CK is out.

not sure if this will affect leveling up later, depend if level points to get the next level is an independent value or calculated from your existing skill level.