Suggestion

1. Sounds like a good thing to have.
2. Crossbow is already good, it has no recoil and good dmg overall.
3. More grenade upgrades would be great.
4. No reason to buff the dmg, Glock can kill zombies pretty easily and if u get to level 7 u get mac 10 which is a pretty good weapon even for higher levels. It does around 350 dmg for a headshot if I remember correctly.
Also, the tank is supposed to be hard so no reason to complain about it, if u you play smart u can solo even with a lower level.