Pate Plastics withdrew from the manufacturing of fiberglass fuel tanks because there was no remedy for the problems of using alcohol-diluted or ethanol-diluted gasoline fuel in them. The resins used in the laminate could not tolerate gasoline blended with alcohols, and the laminates tended to dissolve and mix with the fuel.
Can [a fiberglass laminate fuel tank with a large crack] be repaired and how?
Fiberglass laminates can be repaired without too much problem.
To learn how to repair fiberglass laminates, see several articles on those topics in the REFERENCE section. You could repair it yourself or hire out the repair. I don't see the repair as an obstacle. The repair is not the problem. The problem is fiberglass laminates have proved unsuitable for use with ethanol-diluted gasoline fuels. And in the USA avoiding ethanol-gasoline blended fuel for boats is almost impossible.
Considering the cost of modern outboard engines and the damage that could be done to them from using a Pate Plastics fuel tank, I can't see any reason to want to use a Pate Plastics fuel tank, and even less reason to want to use one that has a large mechanical defect.
Suggestions?
On that basis my suggestion is your damaged Pate Plastic fuel tank be discarded as a fuel tank and some other use found for it.
You could also offer it for sale; perhaps someone would be interested.
If you NEVER use any sort of gasoline with alcohol content, and if you have NEVER seen any occurrence of a problem with the tank, then you could try to repair it and use it.
Also, current EPA regulations of on-deck gasoline fuel tanks used on boats require particular methods be employed for preventing venting of gasoline vapor into the atmosphere. This also tends to diminish the utility of a Pate Plastics fuel tank, as it is unlikely to be in compliance with EPA regulations.
There are a few companies that manufacture fiberglass fuel tanks for gasoline, but they do this for aviation. Aviation fuel contains no alcohols. I believe use of alcohol-gasoline blended fuels is prohibited in any aircraft engine. Thus aircraft with fiberglass fuel tanks will never see fuel with alcohol in it.