(I have moved your thread to the InDesign SDK forum).
Well, congratualtions getting the debug build. By all accounts that's the hard part.
It sounds to me like your installation is faulty. You should not be missing FONT MANAGER.RPLN and SING.APLN, plugins which should be installed by the debug build installer.
Did you update to 18.104.22.1688D, or are you still runing 7.5.0? The update might help.
Otherwise I would uninstalland reinstall.
Visual Studio doesn't sound like it is related to your problem.
the errors about the Font Manager and SING plug-ins are usually seen when VS2005 SP1 isn't installed. That behaviour is a known issue in CS5/CS5.5 debug.
I'd suggest that you uninstall InDesign and all your Visual Studio versions, then reinstall them in the order:
Visual Studio 2005
Visual Studio 2005 SP1
Visual Studio 2008
Hopefully this will get you up and running.