Fish, your Dad's Camaro, whatever Chevy called it, is a hatchback. Ford called its fastbacks SportsRoofs, though they continued to use the term on semi-fastbacks such as the '70 Torino.
Your definition is almost 100% correct. It has nothing to do with the length of the decklid after the glass; if the glass goes up it's a hatchback, and if it's got a separate trunklid it's a fastback. To further the standardized industry lingo: if the glass goes up with the decklid, the car is considered a 3-door (or 5-door in the case of a four-passenger-portal hatchback). I detest the terms "3-door" and "5-door" but they're the industry standard. I don't make this stuff up and it's not just my opinion.
No, 69.5, a FWD Daytona is not a fastback. It's a 3-door hatchback, just like the TC3/024/Charger/Duster/L-cars (as well as the 2-door P-body Duster/Shadow/Sundance, which had more of a notchback look but the glass still goes up) and Conquest/Starion. You can use whatever terminology you please personally, I'm just telling you the standard parlance of the automotive industry. The trunk on a Daytona is in the neghborhood of 4 feet in length... because the definition of the "trunk" (actually "hatch" in this case) includes the entire access opening, which on a Daytona extends all the way to the roof. If that little bit of metal panel opened like the trunk on a '67 Charger, then and only then it would be a fastback.
What really pisses me off is brands like Mercedes-Benz and Audi trying to muddy the waters: there is no such thing as a four-door coupe. Coupe=couple=two, as in number of doors. Yet manufacturers are now trying to claim they build such a beast. No, you don't, because it's not possible. Marketing fucks trying to get sedan haters to buy fast-roofed sedans, some of which are hatchbacks (which Americans hate overall).