For #1: I am only going to skip the last segment, so there will not be any residual value regardless because I consider it a "throw-away" segment anyway. Since it's OW, there is no return for CO to cancel.
For #2: That's actually what I am more curious about. I have never done it before and I don't plan on making a habit of it. I am only considering it because that would make the fare more palatable (not cheap by any means!) as opposed to ridiculous.
LAX
One way is likely refundable and changeable, so it might be worth checking on that....