The rust/rot spot top centre does indeed look like acid burn.
If the back edge is too far gone to sew or glue you might be able to do a neat job with a length of ali angle with a strip on top to make a sandwich using pop rivits. A bit of a challenge. You might surprise yourself how good it turns out.

I expect I'm not the only one who's found a handbook in its blue folder and then found that it's badly damaged by water. That's because they were usually kept on this shelf and suffer from the leaky screen.The water always seems to run along the lip under the dash and drop straight onto the shelf.