Jeannette beat Johnson only once and that was by a DQ. His record against Johnson was 1-3-1 with 3 no-decision bouts.
Young Peter had 60 KO's in his 82 wins BUT he fought 149 times, I think you should count that too.
As far as Dempsey getting knocked out goes, just read this:
Did Jack Dempsey Take a Dive?
Back when Langford, Wills, Jeannette fought they fought each other many times and fought a lot more bouts by doing so. They even carried each other at times. This was the only way they could make any money.
Its very hard to rate someone who you never saw box. A lot of people look at Harry Greb boxing and they say that he looked like an amateur.
As far as pound for pound goes, you would have to rate Langford, Gans, Greb and some others right up their, BUT again, there is very little film on them. I would also rate Langford the best overall boxer that never won a Title. Charlie Burley I would put up their as well.
By the way, we are honoring Joe Jeannette in New Jersey again and I am one of the guest speakers. We did the same thing many years ago and I was the MC of that too.