Most people at top tier can take a few strikes from that without being KO'd. Since Whitebeard used to rival Gol D. but has fallen significantly below his prime due to old age and sickness, Roger's first mate at his prime would likely need to be at least at that level or he's too far below his captain.
I don't think so. They only fought after Whitebeard already got stabbed through the chest and he still needed help to do as much as he did. But I also think Roger was far, far stronger than Akainu before he became sick.
Not to mention, MF Whitebeard was still ahead of Akainu, the strongest Admiral. Old Rayleigh is only about on par with Kizaru who is weaker than Akainu. That gap probably remained 20 years back, and Roger was still stronger than Whitebeard.