In that case roll with what you have and once you zero, you will see just how many mils left you have and will know what your scope's limitations are. Do not try to force that last bit of elevation out though, once it gets tight, stop. Of course you can always hold past that limitation as well; that's what those vertical mildots are there for.
As for the 168's, if you're not hitting the transonic zone (~1300fps, atmosphere dependent) then you're ok. Typically that happens around the 800yd line with 168 FGMM but will again depend on the atmospherics and muzzle velocity. Inside there? Awesome bullet to shoot and usually a more economical option as well.