I have Coat It on the bottom of my glass DB. This looks like what's on the bottom of mine. I mixed and applied about 15 years ago. It did turn to the grey color over time and the rock scratches are a lighter grey.
Your photo shows a VERY thick layer and I suspect this has lead to the cracking and delamination problem. As with lots of paints and epoxies "MORE IS NOT BETTER". These coatings flex with the substrate when in thinner layers. The bottom of my boat is aprox 1/16" coating and it does flex. No cracks or delamination problems yet. I believe the aluminum bottoms also flex.
When I get ready to re-coat, I will sand bottom of mine down to glass and re-apply.
Don't have any Idea as to how to repair with the thickness you have and not have the same problem later.