2) I updated, it's my fault, i saw just normal big-hp decay as effect from FF
Now level finished and all secrets revealed.
I thought concrete box with small gap with portable medkit inside also need marked as secret. (I found it accidentally after any other secrets)
At second play-through I noticed many mobs spawn literally from nowhere. Some can be just resurrected by fly guy or jumped, but at least three mob just before invisibility powerup spawns after rest of level was cleaned just at my back... (Yes, I walk in a strange way this time)
Explosive corpse of fly guy near-fatally surprised me...
And I especially like hp-dynamic: you have >300hp+~100ap, but chose wrong way and use medkit at 10hp under fire, then done with it and easy heal by can-pack for 120hp, but 120hp literally nothing if you make something stupid...