[ashlar]

I am having trouble getting the video cache settings to work.

https://kodi.wiki/view/HOW-TO:Modify_the_video_cache

Basically i want to dump as much of the video to RAM as possible.

Is this because MADvr doesn't respect the cache or has its own cache settings? If so where could I find those?

You need to use LAVfilter Source cache setting. See this discussion on Doom9 where kind people explained how to do it.
http://forum.doom9.org/showthread.php?t=...&page=1174

Bear in mind that you will need to use Nightlies, as Nevcariel fixed a bug in them, as explained on that page (and there hasn't been a stable release since).