I'm not sure about DP, but in Advance, critical hits work like this:
1- 6.25%
2- 12.5%
3- 25%
4- 33.3%
5+- 50%
High CH moves raise crit hit by 3 stages, scope lens and focus energy raise it by 1 stage, and items like stick and lucky egg raise it by 2 stages.
So focus energy won't raise the CH...