I'm, unfortunately, likely in the same boat, as far as expertise is concerned. I have a degree in geochemistry, and I agree with your analysis of the assumptions made to produce this model, but all of the projections I've seen until this one suggested the closing of the pacific basin.

Consider that much of the pacific mid-ocean ridge (the only thing preventing the closure of the pacific basin) is already being actively subducted under the eastern pacific boundary. Think about that: the spreading boundary itself is being subducted. This makes one wonder how it would be conceivable that the pacific basin widens in the future, despite the vast majority of the world's active subduction boundaries being along the pacific rim.