Re: cannot compute backend DFP timings
Right, the pixelclock that the 1600x1200 mode requires is 162Mhz:
(--) NVIDIA(0): Pixel Clock : 162.00 MHz
Your hardware is only capable of 112.0MHz. That is further underscored by the fact that your hardware is only Internal Single Link TMDS capable (as Cambo noted).
This isn't a driver bug, its a hardware limitation.