I partially live in NYC so going from LGA> JFK > EWR by car is a total nightmare just by itself.
Unfortunately it sounds like you had some really bad luck like something you’d see in the “out-of-towners.” Im sorry for your ordeal and I do feel for you, but unfortunately bad things can happen like this when you fly. You can be certain Alaska will take care of the trip and go above and beyond what you paid for the trip given what you had to go through. You might’ve already gotten the standard $125 cert sent to you from their head of passenger comfort “Wayne Newton” but if you explain the full story, AS will certainly compensate you for the whole trip I would imagine.
I have to wonder though, if the delay was mechanical why didn’t you just immediately insist they put you on the next flight on another carrier to Seattle out of LGA? We’re you upgraded and didn’t want to take the downgrade? You wouldve still gotten miles for your original itinerary given that it was a delay that was their fault and would’ve saved a lot of heart attack running around the New York area.