I also start a game whit Pontos and find myself in the same situation after a few turn. I agree whit Dumbass (Blitz the bastards) Up to the end my friend... Whitout cheating they never gonna accept a truce. Try to have your army assemble on a bridge or on a montain slope. Regardless you have to unlock every trade agreement you can in order to have a somewhat good economy to support your war effort. Good luck commander