Reverse actors HP MP progression

[Tenkarider]

EDIT: About the first problem still to solve... if a new character joins the party, the strange behavior(HP rise/decrease) will be as listed before only at odd levels, otherwise it will be unpredictable!!!
There will be a further boost to starting HP which i cannot explain at all

Please, everyone(good at hacking, of course ) is invited to help me in finding the solution, not only Edrin, just because he answered me the last questions.
He has to think at his stuff too!!

I tried to figure out in any manner possible how it works that piece of the code, but I'm totally blocked...