Unless one of the other carriers has a last minute sale and you are willing to take that chance and wait, Southwest is probably your best bet for a number of reasons, but you will have to act fast if you want the lowest fare that they are most likely going to have at this point.
Southwest works on a different system than the others you listed (JetBlue is similar). Most of their tickets are initially posted at their best fares available at that time, when those particular flights open for booking. They have a limited number in each category available, and once those are gone, that’s it. You can actually be on their website and have them sold out from under you, unless you’ve pressed the purchase button and completed the transaction in a specific amount of time.
After that initial posting, there can be a lower fare, when specials come up, and when flights aren’t filling. They usually post specials on Tuesdays and you can sign up for emails notifying you of those, along with DING, their daily announcements, which are part of your desktop. You can also luck out, by catching their website when someone has cancelled a flight and that fare becomes open again.
The major advantage to SWA is that even their cheapest “nonrefundable” fares are not a total loss, should you need to cancel the flight. You can go online when canceling and get a credit in your account, good for another flight up to a year from the date of purchase of the ticket. They will also give you that credit, should you find a cheaper fare for the exact flight at a later date. You can also do that online, and they make it very easy inside your reservation. I had to have a rep walk me through it the first time, but have used the feature ever since.
On Southwest, though, the closer you get to the flight, the higher the fare (in general). Once you get 2 weeks out, it normally bounces up to the two highest fares listed. What I’m saying is that should you go for the SWA flight you have found, in order to get the lowest fare, purchase it as soon as possible so that that lower fare will still be there, as it may either sell out, or become unavailable soon.
It’s too bad you can’t go the day before, as there were still fares around $149 available the last time I checked. Also, be sure to check the flight and get the actually cost of the fare, as the base fare is normally cheaper when you do.
The flight you are referring to does stop in Las Vegas and has a 55 min. connection, and the flight will take you longer than some of the flights the day before that are non-stops.
Another thing to take into consideration. It is routine and legal for airlines to oversell a certain percentage of each flight. Be sure to leave more than enough time before your flight leaves to get to the airport, so you will be there before that happens. If you have never flown SWA, be aware that you need to get your seat pass online as soon as they open up the day before, so you will be first in the boarding line as well, they use an A,B,C system rather than seat assignments. They also aren’t charging extra for luggage at this point, unless you go over 2 checked bags per person. You do need to take your own food, as they have no meal service.
I did check out Sacramento as well, as it is about 2 hours from Marin, but all of their flights leave later than you need as well. Concerning your question about red-eyes, they are generally longer flights, generally in the US, west to east, due to the time zone difference. From MCI, you’d be taking off or landing at an odd time, so those times aren’t as much in demand.
Hope this helps. And no, I don’t work for SWA, I just fly them a great deal.