Making skills is not really my specialty and I haven't touched it in about a year.
With all the qualifiers out of the way, I think you are in the wrong file for adjusting the actual effects of the skill.
You'll see on column 16 there's a list of parameters like this:
Stance,200,-1,SKILLBOOST_MeleePowerAttack
You need to adjust the SKILLBOOST_MeleePowerAttack, or more precisely if you want a custom one to make a new SKILLBOOST.
All of these are illogically located in the file Potion.xlsm
I think you'll find what you need in there, just control + F for SKILLBOOST and copy/paste your own entry then rename it.
