I'm torn on this one. On the one hand, you now know that this house is way bigger than you need. You will pay more in heating, cooling, and property taxes for the next 7-8 years. Plus, I'm guessing that you are in a seller's market like most of the rest of the country, so you might be able to benefit from this and somewhat offset your decision to sell so quickly.
On the other hand, if you are fairly certain that you are going to move post-FIRE, it just seems to silly to move twice, especially in light of your current savings rate. I'm tempted to suggest that you stay and then move once you FIRE.
Moving is expensive. Closing costs stink. Then you've got all the costs associated with moving. I personally wouldn't factor in moving three miles closer to your work. Some on here might disagree, but that's not a big enough difference to factor in.
I think whichever decision you make will be fine.
One thought: With a house that size, could you possibly rent a room on AirBnb? Are you in a desirable enough location for that? Any chance to make a it an income opportunity?