What is the best way to replace the subfloor under load bearing wall
If that wall is not a load bearing wall, and from your pictures it sure does not look like it, you could consider just dismantling it temporarily. Then just pull up the bottom plate. This would leave you fully open to replace the sub-flooring after which you can just rebuild that short piece of wall. It is only 5 studs and less and about two additional sheets of new drywall. 

From your other pictures it certainly appears that you have quite a bit of rebuilding work to do already so re-doing that wall would not be too much additional.