2. First Class Lounge: If it were me I'd make sure there were enough "first class" passengers to make a separate lounge just for them worth the permanent loss of space.
There should be more than enough people for an FC lounge. In addition to regular riders who achieve Select Plus from regular running on the Cascades, you've got the Coast Starlight and the EB of course. But unlike the lounge in Portland, the Seattle EB has two sleepers, plus a few rooms in the dorm. That's many more bodies than what Portland would see for the EB.
3. Assigned Seating: I'm actually a proponent of assigned seating for some routes, but the way they do it on the Cascades makes no sense to me. It's all about hurry up and wait. And then hurry up and run so you can find the seat that was specifically assigned just for you at random. Why? I guess it doesn't matter how absurd and counterproductive this is so long as Amtrak is following someone else's orders.
I agree that it really doesn't make sense for people to run to the train, when their seat is already assigned. I suspect that at least for some however, it's a matter of getting to the floor based luggage rack before it fills up and they have to put things into the overhead. Beyond that, short of that oddly American urge to always be first even when it doesn't matter, I can't explain why some line up to wait so that they can run to get a seat that no one else can take.