Personally, that would stress me out, even as an experienced SEA flyer. It's definitely doable, but as missamo80 notes, if anything goes wrong, I think it would be likely to miss your flight.
Is there anything that has an extra stop (not ideal, I know) through a larger airport with my flight connections that would get you there? Personally, I would pay the extra money for a different flight, possibly from one of the other airports, but it depends on the cost and value to you.
I also note I've had a lot of flights that have changed schedule slightly since I booked them just 4-5 months ago, so it is a possibility that flights so far out will change. There may also be flights added/cancelled. Sorry, this probably isn't helping, but just a reminder to be aware.