Yes, I use the out-of-combat healing... I'm more worried about having enough maximum health to survive the combats. It seems pretty random when they leave, but maybe I just don't know what the algorithm is?
EDIT: Huh, turns out there was actually only one more battle between me and the boss. There was so much I didn't even explore though, thought there would be way more combat to go through.
Slut Mode "combat" doesn't do any damage except for orgasm, and that should be more than manageable if you're healing between fights. The enemies leave each time one of them "finishes" with you. As for the map, it is mostly just a straight shot up to the boss. You can explore a bit if you need items or to dodge around enemies, and there's something useful for the boss on the pier toward the end, but otherwise nothing major.
