I'm probably not much help but:
The cabin cruiser is indeed marked by 2 small white buoys.
Close to where you enter the water, if you go diagonally to the right, just a little ways, there are 2 pvc obstacles and a practice platform. Next to the platform is a nice little statue.
Unfortunately, I have not been able to find the car or tractor yet, though the car is supposed to be near the practice platform...
In case you haven't been, when you pull into the parking lot, there is a small, almost hidden driveway before you get to the main parking/beach area. You can pull up pretty close to the water, though there is a steep drop-off/step to negotiate.
The Cape Dive Locker could probably give you the best information. And if you need a buddy, I'd be up for it depending on my work schedule.