That rifle and caliber will do fine. Huge egos, myths and old wive’s tales live and massage each other, in perpetuity on the internet. Doubt it? … Pay attention to the hypocrisy and echo chamber hiding in plain sight on the subjects of rifles and calibers. Two examples I often see when discussing the 7x57 and 375HH… the same crowd who criticize and demeans owners of the 458 WM speak of both the 7x57 and 375HH as near as any caliber to Thor’s hammer as is known in the mortal world.
For reloading the 458 WM, follow the recommended starting loads and work up carefully. Use a chronograph and keep velocity objectives within reason, Forget trying to hot rod any hunting cartridge. Standard factory vels tend to run around 2150 for a reason! Use temperature insensitive powders and pay no attention to ideas of comparing any cartridge to some stupid standard like 80 k PSI…WTH! Watch for high pressure signs during load work up. A 45 cal 450 grain tough expanding bullet loaded to 2100 fps through the heart/lung boiler of a buffalo will do the job. Your average shot distance on buffalo will likely be somewhere around 50 +/- yards.
I would start by getting some good, tough 450 gr hunting bullets. Use a Lee FCD die for crimping. Big bonus if bullet has crimp groove located/designed for the 458 WM length. Benchmark and similar temperature insensitive powders are good powders to try, Avoid slower ball powders even if someone promises a few more fps!
Reliability is the name of the game for DG ammo.
What about a higher BC/SD 416 doing 2,450 (what is that 6,000+ ft/lbs E?) I, and many others (including KR's recommendations) will take the latter. 
As a plus, I love the Jeff case for wildcats. There's a GREAT video of Capstick shooting a 577 at elephant showing what the gun does to both animal and elder shooter's body in slow motion.
