If you can manage to cut open and reweld the muffler pretty cleanly, a repack may be worth trying. It seems like the Q300 mufflers are super hit-or-miss in terms of how long the packing inside lasts.
As an alternative, you could put your OEM midpipe back on (if you still have it), and pair it up with a quieter axle-back exhaust setup.
I was in a similar situation to you last year. Long highway commute meant my setup of long tube EL header + Invidia R400 was a no go - complete drony mess. To solve that, I threw my OEM catback back on the car (which I kept) and sold the R400. Drone was gone, but so was any sound character.
It took me a long time to find an muffled axle-back option that let me use the OEM midpipe to keep drone down, was reasonably priced, and sounded good without being too loud - but with DC Sports releasing their axleback this past spring, I finally found something that filled that void perfectly.
I've had it on the car for a while now and I am still very satisfied. Zero buyers remorse there. Sounds awesome while being perfectly livable and doesn't drone. Very OEM+.
https://dcsports.com/collections/sta...44374969909500