Just translate it literally, it’s already pretty obvious to hear when it’s being spoken in a slang

So change it so that characters who use slang don't use slang anymore? That's ridiculous. And by the way, most anime viewers aren't going to know enough Japanese to know what is and isn't slang just by listening.

there IS A PRETTY FUCKING BIG DIFFERENCE between a Lolita Complex and a pedophile

Welllll in the example provided it sure looks like "lolicon" is what you call someone when they've broken into a school and you think they want to sexually assault the students so maybe they're not as different as you suggest.