I've made it to the top once, with Smoochum. Really though I found Zero Isle South harder than this dungeon, although it could be my luck. (I did do a lot of Sweet Kiss shenanigans x3)
Moves that hit an entire room are very helpful. Smoochum got Powder Snow really early, so the surprises like Monster Houses and exploding Drifblims were easier to deal with.
Never let your PP drain for too long. Traps and Monster houses (like those on level 14 and 46) are everywhere, but Max Elixers are surprisingly common. And more than half the time you'll see that the hunger bar is the real problem. Eat cherries, eat seeds, heck even grimy food but don't let it creep up for too long. Apples are kinda rare, so grab one whenever possible.
Robbing Kecleon is another way of getting fresh fruit.
That's all I could think of, the dungeon is hard and long so rest in the middle and collect your thoughts whenever you feel worn out. Oh and be careful on the 90s, there are gosh darn Perish Song Politoeds there >.<, and I'm telling you you'll never forgive yourself if you succumb that close to victory xD.