To change the seed of your map, you just open in notepad then file HiddenLand.map, the you search for the line: Seed=hkibxxxxxx, then you change the these 10 random leters to another diferent 10 random leters like this: Seed=X0pHKFnXCs. save and export and now you can enter your map again.
WARNING: changing the seed number will make another map instance in the server, so people in the same map name can not see or chat with people in the same map with diffferent seed.
I mean with this, people in a map with the old seed can not see people in the same map with the new seed, just like if you have done a new different map.
About to get unstuck the char, the only thing you can do is to wait until a server restart.
So i recommend to wait a few days.