I already pointed out the energy is a game mechanic, plain and simple
<You could say that about any game
I can, doesn't necessarily mean it's wrong, you can't say he doesn't use a passive ability because he hasn't been shown to spam it (He'll he only gets it within the last part of DMC2). It's a passive ability, that's how they work.
<Won't do much because Shadow has higher Durability
That's just a bit much, yes, Shadow has higher Durability then Dante, but not enough to where a Slash isn't going to hurt him.
Shadow is>>500 Pettatons for being stronger then his previous form.
Dante is>>>>>Argosax who is>>>Sparda who is>>>Mundus who is>>>172 Pettatons from a casual Abigail
Assuming a minimum lowball of saying he's 200 Pettatons which is ludicrous, Shadow is still 3x stronger at most.
Anyway, enough on Chrono Heart, that alone isn't nearly enough of a reason.
He can still Stop it if he feels it necessary, has a far higher Arsenal of weapons, and is much, much more expirienced and skilled then this version of Shadow, dude has literally decades of experience fighting Demons on his level of around it, and is still alive and well, this is of course on top of him being able to master new fighting styles and weapons on the fly, but that's less important.