Id love to hear the answer to number 3 as well. I can't figure this out either - last time, also, at a kiosk, i never even saw an auto check in reference, yet still was auto-checked in for the return.

For number 1, yes, that is the only way to get included in CPU in advance. Otherwise, you'll be excluded, but can pick a companion at the airport, and you and the person you picked will go on the airport list. I suspect if you split ahead of time, the other 2 might stay in E+ initially, but very well may get kicked out later in a sweep (I.e. consider the event they stay in a bonus).

As for being split, if you get cleared in advance, you shouldn't be split - you will both be in F on the same PNR. Youll be split only if you add yourself to the upgrade standby list when checking in. You can also both decline to be added to the upgrade standby list, and you'll still stay on the same PNR. However, IME, if you choose this option, you'll be included in CPU on the return, but if not upgraded by check in, you won't be able to be added to the upgrade standby list when checking in on the return and, it will be a hassle even for an agent to do it.