I would start by making a few more of those rockwool 2x4 panels and using them as a ceiling cloud. Start with covering maybe 20% of the surface area and see if that knocks down the resonances to a comfortable level.
But be careful how much surface area you cover because it can quickly get uncomfortably dead. My studio space is partially finished, and all of the roxul is currently exposed before we get drywall up. It's amazingly dead, and very disorienting when I step into that room! I wouldn't want the final acoustics to sound like that for sure.
Also be careful using carpet for acoustical control. It only dampens mid and hi frequencies, leaving the lower frequencies untamed. Things can sound muddy or boomy in such a circumstance.