To lower damage of Cross Impact :
In src/map/battle.c,
Find:
/**
* GC Guilotine Cross
**/
case GC_CROSSIMPACT:
skillratio += 1050 + 50 * skill_lv;
break;
and edit
"skillratio += 1050 + 50 * skill_lv;"
to your liking.
I'd like to help you with the second but that'd just be wrong. Maxing baselevel is really easy, if you can download the svn and compile it + log into your server, you can find out how to use BaseLevel and other simple script commands. I'll link you to this : http://buwinow5.tripod.com/ It may be old but it covers the basics.
Smoke's post in Hom mutate npc help! wont mutate was marked as the answer