Update -- I finally ended up swapping this part out, and it was indeed the "Latch And Actuator Door FLH. (Left, Front), Part num: 61032AJ01A". My driver's door locks and unlocks like a dream now, with the door switch and the remote.
Also -- just a helpful tip in case anyone else has to do this: before taking the old latch/actuator piece out, you'll want to remove this bolt, right here (see picture, I'm pointing to it).
This bolt secures the bottom left side of the window channel as the window would roll down, I highly recommend removing it temporarily to allow you to get some play in that channel piece. Otherwise, you would have to maneuver the entire latch/lock assembly around that channel, and trust me, it's nearly impossible. This will also likely turn a 2-hour job into a 45-minute one.
https://imgur.com/a/Vp2N4V4