Maybe try automating things, like mob grinders and automatic farms. mads can be fun. and there are many tutorials for everything. maybe make a giant castle or go into creative mode and code some fun things like a working economy
I'm sorry, you're screwed. just like most IT technicians would say, have you tried re-installing the server client. chances are there are conflicts. I dont know much about crash reports but that's my advice
You can upload your server map to you're minecraft folder, then use world edit to copy and paste in your castle from your world to the server, then upload the map back to your server.
If you have any trouble, please respond and i can go through detail