You cannot interact with npc states that control knockback or inv frames in 2.50.x. You can force the enemy xy manually, as a hack, but inv frames aren't something that you can read, or set, in ZC < 2.54 (some Alpha).
In the latest builds, you have npc->InvFrames. I might look into a knockback boolean, and of course add npc->Knockback(dir) or (angle), along with npc->Hit(w_type, damage, dir).
HP/Heart and MP/Block are internal engine constants. At present, there is no way to change them, although it doesn't seem overly difficult to add that as a future feature. I scripted my own HP and MP mechanics to bypass this in 2.50.
*sigh* Oh well, I'll just have to deal with it. Of course at the rate I'm working on this project, We'll be well into a new version of ZQuest by then.
Lost my wings and grew 8 tentacles... I've seen enough Hentai to know where this is going....