Im guessing that the barrel has been removed by this point but Ill add a method that has worked for me in case someone else runs into this.
A large crescent wrench that fits the recoil lug can help to hold the action, I use tape on the inside of the wrench as well as the action itself. I line my vise (regular bench type) with a piece of cardboard and some strips of thick leather. I get everything lined up so that the wrench is resting on the edge of the bench and tight against the recoil lug. Then I crank the barrel down as hard as I can (dont use a cheater bar) as long as it doesnt slip you wont mark it up. I put a 18" breaker bar on the savage barrel wrench and lean into it slightly to make sure all holds well. Then its a matter of applying enough force to break the nut loose. They are very tight from the factory but once you get it off it will never get that tight again unless you ate spinach for dinner.
I have heard of a method where you simply align the crescent wrench and barrel wrench so that when set on the floor they hold the action up 3-5" (think like a little a-frame) then step or hop on it slightly.