How long before my flight should I be at the airport to go through security and check in on Southwest airlines?

At least 1.5hrs prior to the time of boarding... daily road traffic on highway will also determine travel time to the airport

Agree 1.5 hrs prior. Also to save you time, don't use the curb lane if you see alot of traffic once in the terminal area. Stay to the outside center island area, faster to stop, drop off your pax and leave. Less chances of getting blocked in and or having someone hit you. It can get VERY packed, with 2 to 3 lanes of parked cars as folks are dropping others off.

At least 1hr .30mins before boarding, consider traffic on the highway especially 85 and 285 routes will determine travel time to the airport.

2.00 hour

All the comments above answered the questions. In addition, consider distance of travel from your location, traffic on the Highway, traffic at the airport before drop-off, TSA screening - due to COVID19 their might be slight delay because of "Social Distancing" and time to locate the Gate to board the flight. So I would say 2hours, Another tip here, Southwest airline Gate is located at concourse C and the tickets counter is located at the Terminal North or Terminal N.