UPDATED POST (I was away too long to change my post)
The upgraded JT3D improved the BUFF's performance over the original J57s. With the J-57s, the BUFF performance was outclassed in nearly every way by the TU-95...so, as contemporaries, there was a lot of concern. With the engine upgrades in the 60s, that changed...but only a bit.
The range numbers and payload that you quote in your post sound a lot like Wikipedia answers. I have different sources, though I am relying on my memory, which could be suspect.
10,000 NM is a specious number. Ferry range is interesting, but pointless in operations. Combat radius is what matters - the combat load changes airplane performance considerably. Ferry is for show.
Tactically, .67 and .72 are the same speed. You can often tell the design cruise speed from the sweep of the leading edge...and the a Bear and BUFF have very similar leading edge angle.
The BUFF needed in flight refueling to strike the USSR...But the Bear didn't need it in order to strike the US. Ergo, greater range for the Bear.
The 80,000# load you quote for the BUFF is off too. It's closer to 70K, and when you put wing mounted stores on the plane, the range decreases considerably, just as loading AS-4s on the Bear dramatically reduces its range.
I'll grant you the higher altitude for the B-52.
In a maritime surveillance/interdiction role, the Bear has greater loiter than the B-52. A tactical advantage.
It's easy to look at the Bear as outdated compared with the B-52, which is itself outdated, but there are things that the Bear does better than the B-52.