I haven't tested these, but found the exact values here (I'm pretty sure this is the quicksave area):
0x1C187-0x1c188: Team Member 1 Current Health
(Yay, no bit shifting!)
0x1c189-0x1c18a: Team Member 1 Max health
Additionally, in PkmnEx, HP2 is the max HP, and HP1 is the current HP at the time of entering the current floor, both as shown by the game.
I'll update this post when I have more.
[edit]
By the way, you can safely have your held item editor access 50 items.
There's 100 held items, 50 for the main story, 50 for the special episode. The 51st item is the 1st item of the special episode. 49 and 50 can hold usable items, you just can't fill those slots in-game.