I suppose it does terrible dmg because of your low skill, since you are frequently hitting non vital body parts and/or grazing enemies.
Are shady zombies the ones that turn invisible during the night? I never had a problem with them since I only encountered them around the late game, but I would use hallways and windows to your advantage; in other words funnel them into areas where you know they are going to be and fight from there.
Not entirely sure, but checking near riverbanks would be a good idea (this is based on Minecraft knowledge lol).
Mines are definitely a mid/late-game thing, completely unsuited for a survivor like you as of now. They require quite a bit of preparation, most of which you probably don’t have. Most contain very unique things, but I don’t want to spoil that for you, so steer clear of them. And as for your regard towards gathering ore, if by ore you mean metal, then that is generally done above the surface. Usually when you need metal to craft you strip apart car wreckage or find lying around destroyed cars. Much easier than mining and smelting.
Using cheap ranged weapons like slings or guns with low caliber bullets (such as the .22 Marlin) are good ways to start leveling up marksmanship, for example. The crossbow is not a bad choice (assuming you want to keep leveling it up), but an alternative early game staple that many survivors (such as myself) enjoy is the pneumatic rifle. I think you need a decent amount of parts and at least 6 fabrication and 2 marksmanship to craft it, but the ammo is cheap and plentiful and it is virtually silent, 2 invaluable things for a starting game weapon.
Hope this helped 
