I had no problem inserting the head unit into the Metra dash kit. I fit perfectly. That JVC unit is not slightly oversized - however, I think because there is no trim ring with the unit, the faceplate can use more available space, even with the standard 1 DIN sized unit behind the faceplate.
No solution to the steering wheel controls yet, they do not work, and I'm not happy about it since the remote control for the JVC unit is AWFUL. It's got about 4 thousand buttons on it, and the ones you use the most are not easy to find (power, volume, source, up/down preset, etc). Whoever designed this remote control was probably thinking of a user who could spend 3 full seconds staring at the control before pressing a button. 'Kinda hard to do when driving for most people.... maybe JVC makes a smaller, more user-friendly remote that is compatible with this unit.