I agree with most of your statement, but you should note that Gai wasn't even trying to kill Kisame when they last fought. Testament to his badassery if you ask me, capturing Kisame who he himself captured numerous Jinchuurikis.Oro with low difficulty.
Gai's ultimate attack was tanked by kisame who himself is one tough cookie.
But oro is way tougher and with the rebirth teach he can shed his skin and heal his wounds.
Gai doesnt have anything which implies that he can beat oro
im not sure what you are trying to say by bringing up kisame and jiraiyakisame<jiraiya (power- 35.5)>oro (35) by a little so kisame isn't as strong as a sannin
so oro wins with major difficulty unless gai goes eight gates and ends the fight quickly but then "bites the dust" right after (the only problem gai would have is that oro isn't really affected by physical attacks-cut his body in half he just reattaches) 0.o