We'll need a little more info. Describe the range of up and down tempeature swings - warm, 1/3 scale, 1/2, 2/3 - and how rapld the swing is, and how often it happens. For a Daytona with unobstructed radiator and heater core, and everything in good condition, it should not go above the halfway mark except in desert heat while idling. Normally it should be in the 1/3 to 1/2 scale range.
You might have a plugged heater core. That won't account for the coolant leaking at the radiator cap, though.
Has the system been serviced recently? A trapped air bubble can cause lukewarm heat and uneven gauge swings.
Also, are all of the hoses hot to the touch when the car is warmed up? One heater hose should be VERY hot, the other reasonably hot, after a drive. Top radiator hose should be hot all along its length.
If the radiator cap squirts out coolant, that means that the pressure has exceeded its 16 psi relief rating, or the cap is defective, or the overflow line to the jug has plugged. It can also mean a failing head gasket, whereby there is a compression leak between a cylinder and a coolant jacket, and the running engine is pumping exhaust gas into the coolant. This will show up at cold idle with the radiator cap off, as a steady bubbling at the top of the radiator.
Does it still idle smoothly? Is there any smoke out the back? Are you running a 50/50 mix of antifreeze and water? Is it a 195F thermostat in the engine?