Thats weird because 76% is usually an emulator issue, the only thing else that comes to mind is your missing some kinda variable or text, maybe :s hopefully someone with more knowledge on Habbo clones can give there input here
Next is to check your emulator, make sure your client has the correct connection details and the emulator is allowed through your vps firewall, i know some vps block all but the common ports for security reasons, also check your vps os/windows firewall
I personally believe both are you in the wrong, he doesn't need full access to the VPS via remote desktop but he does need some resources, database access, file access, etc that is why FTP and MySQL are awesome, plus you can create custom users to allow what you want each person to be able to do
From my understanding editing them is virtually impossible atm, the issue is there is no decompiler support. Your time would be better spent, recreating a old school retro client in your desired language.
I can see them just going the mobile route, and maybe a desktop app, for some reason I feel like They would shy away from HTML5 to keep clones away as much as possible