The 1.5x3 frame bend looks good, that's a weak spot . The two rectangular pieces on their sides are normal they are the frame for the where the normal frame is cut away for the walkway. There is a piece of wood attached (glassed) to the frame ear and attaches to the shell in the front area of the walkway. The piece of wood can rot out causing the sag. It looks like your wood block may be rotted and fiberglass may be cracked where it attaches to the shell. I'm not too sure what's going on with the vertical metal plate that may be cracked.
I would try to align the shell and replace and glass in wood block before ripping out the front floor. There are four upper floor sections in a Scamp
, only replace one section at a time or the shell can get out of whack.
The wood block is the height of the frame ear and one end is cut to the contour of the shell. The wood block is screwed to the frame when everything is aligned glass it in with glass mat.
After looking at the pictures again it appears something has hit the two lower frame tubes and compressed and cracked the vertical metal piece. I would straighten out and weld the crack in the vertical piece. I think the sagging is caused by the bad shell connection and the wood block. This is my best guess by only looking at pictures.