A key question of the crew reaction is “were they following the Airspeed Unreliable checklist?”.
From the FR24 data, it appears that they were not. There is no attitude and thrust data in the QRH that provides level flight at 5000 feet at approx 300 knots. (Not on the NG anyway.)
So what were they doing?
If they were flying “an” attitude and thrust, that would automatically include manual trim, which would eliminate the MCAS issue, with a possible manual trim input every 5 seconds required.