V.W fit different versions and features MFDs according to the 'line'. Yours is probably Hi-line whereas my low/mid line without your wheel buttons only gives basic information. What extra information from the MFD do you think is missing? Have you got an EOS manual in the glove box tray? That should cover the MFD.
I'd expect your wheel to work with the dash MFD as V.W designed it, but the interface to a non OE Kenwood unit may not be fully V.W compatible, although it sounds from what you say that wheel buttons are controlling the radio? If you are expecting buttons like a home button to work, then that is down whether Kenwood included that control feature, They do say they offer the opportunity to control the head unit using steering wheel controls. That may not mean fully compatible. Kenwood are a reputable company to contact if you think some wheel buttons have no function with the DNX520VBT.