Sorry to bug you
I think there's a couple of things going on here.
Concerning the famous Unhandled Exception, you're right - it can't find SDL. I believe the package you need is
libsdl2-dev. At least i get a
System.DllNotFoundException: SDL2.dll unless that one is installed, but once i have that, it works without modifying the Monogame.framework.dll.config.
You don't need to actually install Monogame, but i'd make sure to install the latest version of mono from here: http://www.mono-project.com/download/stable/#download-lin-raspbian.
mono-runtime should be fine, but i think i'd install
mono-complete just to be sure.
If you are going to use audio in your project, specifically the
SoundEffectInstance, you're gonna get in trouble, as the version of OpenAL in Raspbians repos is quite outdated. However, you can compile the latest version from source: https://github.com/kcat/openal-soft. You can then link to your compiled version of OpenAL in Monogame.framework.dll.config like this:
<dllmap dll="soft_oal.dll" target="/home/pi/Downloads/openal-soft/build/libopenal.so" />
That works for me, at least.
Not so sure about winforms - i actually thought that would rely on user32.dll and thus not work on the pi, but you got that working?
Concernong touch, i'm afraid i don't know whether or how it works, as i have not used it.