It is very easy using relays.
To reverse a motor using relays, you do not use a "reversing relay" (DPDT). You use two SPDT relays, one connected to each motor terminal and each switching from ground to 12 V or whatever. Actuate one relay and the motor runs forward, actuate the other and it runs back. The limit switches are in series with the relay coils.
Of course this does not protect against relay failure. 
But the relays are only energised while the motor is running.
Thanks for the suggestion! I think I'll lose speed control if I use relays to actuate the motor if I understand you correctly.
I was looking at using a relay that was controlled by the microswitch, but I think the relay will be energized while the switch is closed. Most of the time, the actuator will be at the limit (at rest), so I don't think that will work well for battery.
So, my options so far:
If anyone has suggestions on #3, I think that may be the better option of the 4. I would get software and hardware control... and sending a 0 to the motor driver speed should cause the motor to stop immediately. Again thank you!
OK, to do that you need some logic. You need to AND the enable with the status of one of the limit switches selected by the direction input.
A 74HC253 will do this perfectly (you use only half the logic). 
It has two select lines, selecting between one of four inputs, so one select line is your motor enable, if it is not enabled, then two of the four inputs that may be selected are wired to the motor "off" state. If it is to be enabled, then the second select line connected to the direction input of the motor driver selects one of the two inputs which are connected to the limit switches (which have a pull-up or pull-down depending on which way you need to enable the motor driver). The output of the selector is then the actual enable for the motor driver.
So you have the limit switches working at logic level, drawing negligible current (depending on the pull-ups and they themselves may be switched by the enable depending on how the logic suits) but the pure logic chip is totally reliable as it cannot suffer from a code crash. 
Thank you so much for the help! I'll post my updated schematic once I do some more reading on the datasheets!
I ordered the CD4081BE on Amazon. I attached my revised schematic which should hopefully work!
I also wanted to add I'm using the Pololu carrier board (thanks to chip shortages). I didn't bother connecting all the inputs to the VNH5019.
@czu001: Please ignore this uninformed comment:
you are not using limit switches like the rest of the world uses them?
I, and many other people in the "rest of the world" use exactly your setup, with "hard" limit switches in the motor leads. Many linear actuators, such as these ones, come with that setup built in. It protects the motor, motor power supply and the rest of the system from damage in case the controller or driving MCU fails to read the "fluff" limit switches, or they themselves fail.
The motor controller itself can tell you if one of those limit switches has been tripped, because the motor current sense (CS) output will drop to zero.
Hi,
Polulo Carrier;
Tom... 
CD4081? Might work, but obsolete!
