I've made some changes to your mod just for my personal usage to test game pacing on 120 min cycle. Changes include slower exp gain for construction tools and mining. I also moved some bow, pistol, rifle crafting unlocks to later levels. And moved concrete working, iron working, steel smithing to later levels too. I also lowered Quality Joe's effect. And halved EXP gain from zombie kills.
Now, I noticed something strange, don't know, if it's the vanilla game function, your mod's or my changes' effect. Hope, I'm not out of the line, asking here
I maxed mining tools to 100 (it had happened before I made above-mentioned changes in files), now, it seems, I'm getting player lvl experience when I destroy rock blocks while mining underground O_o . I.e. each terrain block gives me quite a nice bunch of EXP. I've made a level, working with an iron pickaxe for 3-5 minutes. There were no skill lvl ups during that time, because Mining tools are maxed out, but I gained a charachter level. Is anything like that supposed to happen?