Greetings.
I like the current hit system. To me most of it makes sense.
I think the hit is on the first look pretty strange.
But if you think about it, it’s starting to make sense.
If you are fighting with a pocket knife against a zombie, you need to get really close and personal to hit it. You would probablly need to fokus more on defense, and therefore it would get harder to hit the zombie. Therefore, cutting an opponent with a small pocket knife will probably be hard. Hence the -1 to hit.
A pot on the other hand is a bashing weapon. im not sure if i would give it a +1 to hit. more like a 0. But you can just bash at the enemy, without needing to place cuts.
Baseball vs knife spear I would leave it as is. Hitting something with a baseball bat is pretty easy (except if your actually playing baseball :-P)
And the Knife spear is a weapon made for stabbing, but like i said before, stabbing is still harder to do then simply bashing at an enemy.
Also, the better you get at handling the weapon, the less the -hit is going to matter, so you will get better at handling the weapon.
If you hand me a pocket knife, and tell me to stab that dude over there (putting aside the moralty stuff), im pretty sure i would da a pretty bad job at first.
Give me a Pot, and i pretty much already know how to clobber stuff with it 
It’s not perfect, you could argue that some boni and mali are kind of strange, but on the other side there are a lot of people involved in that project, and everyone’S opinion will be slightly different.
No idea about the STEN gun issue, i have no experience with guns.
Hope that Helps,
Dawn