I think you're right in that I shouldn't have said he has a decent shot at making the NCAA 800 final, but if the races go out slow, I think that is to Beach's advantage. He's 18th on the NCAA list so at least getting to national wouldn't be a huge surprise.
I'm not a multis expert, but I follow the dec/hep fairly closely. If Clay finishes the dec without any no heights, DNFs or three fouls, Beach won't make the team. But if an unfortunate event befalls Clay, that opens the door for several other decathletes. It's true that Beach's score will certainly be hampered by his weak throwing events compared to his competition for 3rd. But he's capable of beating all of his main competition by at least 20-30 seconds in the 1500. A 30-second advantage would give Beach about 200 points more than another competitor. He should be ready to run at least 3:55 because I would bet that's what it will take for him to make the team if Clay falters.