Short of more work than you wanted, obviously taking apart to rebuild would be option one. However if it were mine and continuing with direction youve gone what I might do to spread loads.

-Remove added metal framing bracket.
-Pump the delaminated plywood with glue, clamp let dry
-Cut as large a piece of single plywood that will fit inside thru hole to make a single backup 'L' to inside of hole. As far back along the bottom and up as high as you can up front corner. Notched to set on new bottom ply. Profusely glue and screw new 'L' piece to existing backside of hole.
-Remove the campers plug, remove the 2 forward carrage bolts.
-Replace the carrage bolts with bolts going up thru bottom-nuts inside. (welded to bar or plate would be good)
-Cut as large as will fit another piece of plywood to fit against front wall. Notching for wrench clearance to access nuts/upward travle of bolts. With as much contact with bottom ply you added as possible and contact with as much of front wall. Glue and screw to front wall.
- bore hole and rewire plug.
- The aluminum angle would be good tying corners, Could use 2x2
just some thoughts...