Cut the top tabbing off, use a multi-tool with a half moon blade to cut it flush to the wall. Clean the wall with a twisted wire brush where you intend to attach the upper tabbing. I usually trim the bottom tab (To about 1") to clean up the rough edges. I reuse the bottom tabbing and reattach with resin. If not tight to the flooring I use 1/2" self tapping screws to pull it tight after resin has been applied.
After the bottom has set you can fill the gap between the wall and floor with thickened resin or just attach the upper tabbing like Scamp
did it. When putting the floor in put adhesive sealant on the floor metal upper lip. You can attach the floor to the frame with counter sunk self tapping wood to metal screws. Even though using self tapping screws drill pilot holes. I don't use OSB, I use 5/8" plywood (4 green bars). Clean and paint
your frame while you have it opened up
Since the rear floor issues are caused by a bad rear window seal. I remove the back window prior to the repair process and reinstall it after all work is complete.