New to Alaska Airlines so looking for guidance on seating. I purchased a "premium" seat as I wanted the extra legroom for working on my laptop. Now it appears as though I can select an Exit Row (this was previously not an option) but am confronted with a warning "Switching from an upgraded seat to a main cabin seat means you will forfeit your seat upgrade fee and miss out on the inflight benefits of your upgraded seat."

Multiple questions:
1) If I select exit row, can I go back to my "premium seat" without paying?
2) On this 737-800, is there extra legroom in both rows 16 and 17? Is it more legroom than a non-exit row premium seat? This is a daytime flight so I don't care about the non-recline in row 16.
3) If I select exit row, do I lose my early boarding benefits that came with the premium seat (I have zero status / credit card with Alaska)?