14 places apart for me (although my list constantly changes): 17. Ross 18. Moore 19. Ketchel 20. Burley 21. Jofre 22. Whitaker 23. Monzon 24. Arguello 25. Chavez 26. Hagler 27. Hearns 28. Tunney 29. Mayweather 30. Jones Jr 31. Pacquiao
I don't see why not. Ross is top 20-25 p4p all-time, Pacquiao is comfortably all-time top 50 and would in the low 30s for me so really only a maximum of 15 places difference.
No, not a great gap. I probably have Ross a tier above though. Many would rate him within the top ten of his best (deep) weight class, all time. Not sure about Pacquiao. But to have them within ten to fifteen places of each other p4p seems reasonable.
These are the only fighters I have above Barney Ross: Robinson Langford Greb Armstrong Ali Fitzsimmons Gans Pep Charles Duran B Leonard Louis Walker Wilde Ray Leonard Saddler