These are just 100% made of awesome, I found them so helpful and I have already hit up 95% of the technical bugs and mapping errors.
It's funny too, because the version you had I was working on with the skills and the EXP gains and levels, etc. and I think I have it more balanced or more difficult, as you don't gain your better skills so fast as well as HP and stats.

I've also taken into account a lot of your opinions and criticisms and I hope to add and fix some of the issues in the near future.
(Sorry about all the bugs! But thank you for finding them, it sometimes is the obvious things that are neglected when testing)

Another thing is I'm planning to add a system where you'll receive points(money) and you can spend it to make your skills better.(this would help making earlier skills better if you wish, like adrenaline) But I might also look into a shop or sorts, though it would making the balancing harder because resource management is a big deal, so if anything food would just cost a lot of SP(survival points)

I've also thought of implementing a stamina system, just haven't gotten around to it yet. Because I do believe it would help just a little bit. Then again I'd probably make 50% of the zombies faster, just because you would have that burst of speed on them.

There was other stuff I was going to address that I know you asked about, and I'll get around to those, probably just edit this post or something.

Thanks again for these, it's greatly appreciated. :)

edit: Oh, and I'll be updating the download since some of the bugs were game breaking, so it should be up shortly.

Re: the stamina system. Instead of just letting it give you a speed burst and then cranking up the speed on everything else, why not let it give you a speed burst which is slow to recharge, and give you combat penalties if you get into a fight while that speed burst is recharging? I'd rather not have turbo-zombies blitz across the map and mob me while I'm picking a can of soup out of a trunk, and the idea of fighting poorly while exhausted makes more sense to be than every zombie drinking nitro.