I'll address your questions/concerns in reverse.
There is no way to subtract experience from one class and add that experience to another class - it's not part of the game. That said, I can manually edit the database and make the change(s). However, I won't. If I do this for you, I have do it for everybody. It opens a can of worms I do not want to open or deal with.
If, for example, your class lost experience because the server crashed, or because of some fault of Duskgamers, I will edit the database to restore your class' experience. That's something I'll do for anyone.
Regarding killing idle (or knife-camping) players after X seconds, that's definitely something I can do. However, it's not a solution. A player can simply move just enough to defeat the timer/condition. On the other hand, players who are AFK or camping for legit reasons will be killed - which is a problem. Then there is the Ninja class which can only use a knife to level up.
I have considered randomly exploding zombies. This option too has its problems, but I'll think about it. The one common complaint I receive from players is that it takes too long to level up. If I introduce exploding zombies in the server, it will be even harder for players to level up.
As for knifing zombies in a corner, that is totally legal (assuming the zombies can reach the corner). It's a strategy some players use to level up quicker. There are other strategies. Part of the game is to learn what those strategies are, and use them to your advantage.
I don't know what you mean by "safe space". If you mean "illegal camping", which is against the server rules, please record a demo of the player(s) illegally camping and post it
here. I'll ban the offender(s). Alternatively, you can join our Discord server, and message me or Tom.
I know you're a regular on the RPG server and you have played here for many years. You're a good player. You're a good guy. Unfortunately, time spent playing on the server is not the only thing that determines how quickly you level up. How you play the game, what strategy you use, and getting other players to help you can make a big difference to how quickly you level up.
Have you tried knifing zombies in a corner? Have you asked other players to help you?