PPSH-41 and some other weapons like SKS with bayonet are weapons only for NPCs. I just forgot to make them invisible in players inventory. The fact that you can't use them means they work correctly otherwise. Will fix that in next version.
You can only get a blood staff for powers you have, so if you give Zacharias fire stone for the "one of us" quest, you can only pick the fire staff and not the flesh staff. Same works for the flesh stone. If you finish the "one of us" quest, you can still find the other bloodstone and give it to Zacharias later so you can actualy have both the fire and flesh powers. If you finish the bloodstaff quest after that, Zach will ask you if you want flesh staff. If you say no, he will ask if you want fire staff. If you say no again, he will ask about the flesh staff. If you have only one power, he will ask the same question again and again until you say yes.
So if you have only one blood power, then everything works correctly. If you have both flesh and fire and he asks only about the flesh staff, then there is something wrong and I will need to look into it more.