Is the lounge open to all Alaska card holders

Note that your first class ticket can't be an upgrade. It must be a purchased seat.

You need to be an Alaska Lounge (paying member) or ticketed in first class. There are also the reciprocal passes from the other airlines.

You can also use Priority Pass with any Alaska Airline boarding pass. If they're crowded they won't let you in

No. Only if you fly business class or have other contacted cards, e.g. Priority Pass.

Yes, lots of construction and bathrooms were so very dirty sadly