Most airlines (including UA) don't consider "urgency/expense/inconvenience of onwards connection" as a way of sorting the standby list, so it's not really fair to complain that you didn't clear standby. Perhaps the only thing that went poorly is that the UA agent said the standby "looked good" and yet you didn't make it on.

What are you suggesting they should have done for you?

#1 you didn't want to go on the nonstop due to downgrade Premium -> Economy Minus
#2 you didn't want to overnight in LAX due to joining your family for the transpacific flight

What other options are left?

I find it fairly ineffective asking airline staff to evaluate my requirements and recommend solutions. Instead, I educate myself about possible resolutions, and then ask the airline staff to implement them for me.