Not planning to pour the adhesive into the cracks. That might work only for smaller areas adjacent to the cracks.
Also I doubt if the outer composite layer is designed to be separate from the foam-core in this boat. It is just a 3/16 inch sheet and it does not look like it can take the weight of the boat ( 100 lbs ) while being moved by road on a trailer. ( I also get a feeling that some of the cracks might have developed after the sheet separated, because of the loss of structural integrity, especially while trailering the boat by road. )
Regarding adhesive, it is a bonding of a hard composite layer to a softer foam core. Don't need a super strong adhesive, but something tacky, to be applied evenly and uniformly over the entire contact area. (I read about FastBond melting some types of softer foam, in the reviews.) I had used this adhesive to cover my homebuilt airplane ( Mini-Max ) with ceconite fabric 3 years ago, with excellent results, and was impressed with its ease of application. I can do a test patch on the hull foam, but I am sure there are more suitable adhesives.