just a few things i thought i'd mention:
comboing isnt necessary at all. i played on a crappy computer my first time through using an emulator and the best combo i ever got was probably 6 hits, purely out of luck. i'm playing it now and i havent gotten more than 3 hits so far. if you cant combo, you just have to level up a lot and learn to use items efficiently.
emulators mess up the rhythm combo system. it is not nearly as hard on GBS/DS or PSP as it is on an emulator on computer. using a keyboard creates some lag in the button pressing, too. tip: make sure your frame skip is set to 0.
learn to abuse the rolling hp counter (which is actually much much much slower than it was in earthbound). anything that interrupts the "roll" will modify it based on the number it was set on. this means if you end a fight even though you've taken lethal damage the counter will stop. slower characters are often better because when you use a healing item it will heal you from whatever number the counter is currently set on. say, for example you have 30 hp and you select nut bread. the enemy attacks first dealing 10 hp but you ate the nut bread when the counter hit 25; you'll recover up to 55hp instead of 50.
not true. if you take mortal damage, but heal yourself before the HP bar reaches 0, you will have only how much you healed yourself. if you're gonna die but you use nut bread, your HP will be at 30 when it stops. still, the scrolling HP has saved me from a lot of tight situations, and it is even NECESSARY in the game at one point (those who have finished the game know what i mean).