Years of grime in Gel Coat body

[hi-tech cobra]

I’m going back over it with dawn to take as much off as possible before using a wax and grease remover in hopes of creating a clean surface before the sanding begins.

[hi-tech cobra]

How do I fix a fiberglass crack behind the drivers seat in the rolled edge (see pic). You can see the crack open up when you push. So I think it’s more than a gel coat crack. It needs to be strong and support the area. Don’t know how to fix, maybe fiberglass mat and resin? Also how do I address the large cracks in the gel coat? It looks like bubbling between the gel coat and fiberglass.