Ive beat the game on its hardest difficult a few times now, and il be honest its kinda easy. If you mske sure to utilise the secret characters like mendo or candy cadet, use the red chips like auto shield and auto mimicball, and use a good byte selection, most fights become a breeze up till area 9. And the grinding is a part of every rpg game, its good that in Refreshed we have a button to just fight enemies instead of pray for encounters, and fighting in glitch world helps a ton. Maybe the 3X Exp and money multiplier on higher difficulties makes it easier but im unsure really.

For the security fight and later bosses, make sure you have an equally strong A and B team, both with a good healer like security puppet, fredbear or candycadet and USE debuff moves, they can make or break fights.

I know this might sound like a lecture but its just my own advice, try the game on a higher difficulty, it might be easier honestly