Like I said the PiMax headset will support any game controller you can use outside of steam in PiPlay Content.
Inside of Steam it is what steam supports. You should be able to use controllers supported by steam. Now i would reccommend disabling steamvr home.
If you have an Xbox or xbox compatiable controller (logitech controller for example) any program that supports a game pad should work.
The Vive/valve controller by the sounds of it is unfortunate that they made it vive only (by what you said) is terrible on valve side.
The Valve knuckles tho in theory should work with any headset.
As for video. If regular & 3d vid etc. Check steam store there are several free & paid players.
Video 4 vive is reported as a good free one.
Alternatively you can add any program to yout steam library & launch it then from steamvr in theater mode.