As the ticket was sold by Alaska you need to ask them, what's on the Aer Lingus website is for tickets sold by them via the website and is meaningless in this case

If booked through Alaska's website the 10kg carry on entitlement is automatic on all EI metal

Generally its 20kg checked and free seat selection applies to tickets ticketed by other carriers. Seat selection, no exit rows or the first 7 rows of the cabin