You do have the connections correct, but you didn't list the zener diode between gate and source, cathode toward the gate. It should be between 10 and 18V. I'd probably go for 12V if I had to buy one. Since the max voltage between gate and source is typically 20V, you'll soon see why the zener is so important.
Many transients ring both positive and negative. The schottky would try to block the negative part of the transient. As it isn't designed for this, it may eventually fail. If it fails open, then you've lost your protection. I would use the bidirectional TVS, so it will survive the reverse voltage connection as well as the negative part of the transients.
It sounds like you are making a circuit board, so the TVS goes at the edge of the board, right where power and ground come in. The traces that power everything else come right off the pads where the TVS is. Nothing else is grounded, except to the TVS. If not making a circuit board, the same concept applies - all power and ground connections go back to the TVS, and from the TVS it connects to the vehicle.
Now for the TVS voltage. You mentioned 'massive load dumps'. When I was designing a fuel pump controller to meet the requirements of a major manufacturer of construction equipment, their spec said load dump is up to 86V for 12V systems, 172V for 24V systems. Most modern 12V automotive alternators clamp their output voltage at 40-odd volts. A battery in good condition should keep it lower than that (worst case load dump is alternator maxed out and battery disconnected). Pick your poison. The TVS has to survive that. Transients contain very little energy, but load dumps can really pack in the Joules. You don't want to try to clamp one with a little surface mount diode.
Then the FET has to survive the max clamping voltage of the TVS. The LED driver that I sell for automotive applications has an 80V TVS and a 100V FET. Most of them go to off-roaders, so they'll certainly see lots of winch-related load dumps that will overmax the alternator. Nobody's complained about frying one, but they are all 12V systems.
Also remember that the driver circuit needs to survive the load dump voltage. The reverse voltage protection and TVS are intended to let that voltage straight through. That's why I use a 100V FET. It's part of the driver; there is no reverse protection, and the TVS is unidirectional. The one I'm working on now has bidirectional TVS and reverse voltage protection.