I did complete everything, I just couldn't get past the first few regular enemies. Lavos was surprisingly easy so I just went to the Apocalypse or something like that. Took a while, but Chrono/Marle/Frog had good HP sustain so it was easy. I was on my toes the entire time though.
The game is too long for me to replay it, despite it being fun. Maybe in a few years.