2.5 hours before a domestic/european flight

Hi everyone. Flying out of Madrid tomorrow morning with Iberia at 9.05 am.

I received an e-mail saying to arrive at least 2.5 hrs before the flight since many passengers are expected. Flight should be T4.

I want to take the subway from Sol which starts at 6am with an interval of 7-9mins between trains according to the metro website.

Even if I leave at 6 am, I won't be at the airport before 7am. Boarding starts at 8.35am and I only have carry on luggage and am already checked in.
Should I just go with taxi/Uber or you think the timing is okay?