You really don't need to self help disembark at San Pedro for a 1235 flight, owever for the 4 day cruise you probably won't have much luggage. . We book a private car and make it to LAX easily by that time. You can also let the ship staff know you would like an early disembark so you are one of the first off of the ship. However, LAX is nothing like STL for convenience. The last time I flew out of STL, I was the only one in the pre-check line.
With that said, I am one person that doesn't stress out like many if they miss a flight. If I miss a flight I get a later one or just spend the night and enjoy a few drinks and a nice dinner, and leave the next day. I do have pre-check and Clear, so security lines are usually not a problem for me.😃