Traveling at this age is soooo easy!!! You don't have to buy a ticket. He can easily sit (or nap) on your lap. If the flight isn't sold out, they would probably let you bring the car seat on board and put it next to you. I never did that personally, but I know people who have. What I usually did was to try and time flights for around his nap time. I'd bring the stroller and car seat to the gate and check them there. It's very easy.
I'd wear my son onboard in a sling and then nurse him. He'd fall asleep for almost the entire flight. He never had ear problems this way. If you nurse, get yourself a window seat. You are allowed by law to nurse so if anyone gives you grief (which they never did in my case), be aware that it is your legal right. Otherwise, take a bottle and have him nurse on teh way up and on the way down to avoid ear problems. You get an extra carry on with an infant so you should be ok.
With SWA, you can now check in and print your boarding pass online starting 24 hours before your departure. I highly recommend you do this. SWA has done away with preboarding for families. If you have a number greater than 30, you can board after the first boarding group.