Sullivan for me would be the type to use whatever is at his disposal, be it a whiskey bottle, chair or something similar. With his temper and eagerness to go at it, I think he'd take Jeff by surprise and end it quickly.
Jeffries size is blown out of proportion ... I've seen every photo there is of him next to Corbett from every angle and elevation and Corbett was taller. Corbett may have been 6' 2", actually under measured so there is no way Jeffries is more than 6' 1" . In addition, in his big fights he weighted about 208 - 212 . If a prime Sullivan was about 195, Jeffries did not have this huge size advantage ... That being said, both guys were hard core tough as nails and who knows ... I think Sullivan was tougher at the end of the day as few remember Jeffries came from a bit of a privlidged background while Sullivan came from the streets ...
Jeffries is maybe too nice a guy for this brutish tomfoolery. John L via shameless ungentlemanly tactics which could only be described as foul.
In these circustances, I think Jim would apologize and give it to John by default. Nothing to break up that way.
I would be inclined to take Jeffries in a street fight moreso than in the ring. Jeffries was a world class wrestler and if he were able to graple in an unchecked manner he would likley be able to take Sullivan to the floor. It is reported that Herbert Slade got the better of Jeffries in a bar fight while they were engaged in their vaudaville tour. Sullivan was extremely drunk became violent and headbutted Slade. Slade took Sullivan to the ground and was able to hold him down untill the police arived. My guess is that Jeffries would be able to replicate the feat.