if sw3 is pressed at the wrong time or the motor stalls before the limit switches operate (ie door shuts on a chook , fox , next door neighbours kid )you will let the smoke out of your l298 .
those cheap satellite positioners make really good easy to use linear actuators ,somewhat weather proof too.
also you could use gp3 as an input to check that the motor is not stalled (reed sw and a magnet that rotates with the motor)