2018 Outback - windows smell of mildew

I recently acquired a 2018 Outback limited from a private seller. About a
month after I got the car (and the cover-up scent wore off), I noticed a
musty/mildewy smell, which I thought originated from the heating/cooling
system. I cleaned the A/C coil w/ the Subaru foam cleaning kit and sprayed
all the vents, which helped somewhat. But I noticed the smell more strongly
while the windows were down (no A/C or vent in use). An intermittent
electrical issue required replacing the rear passenger window cord, after
which I lowered all the windows to check operation. Again, the strong whiff
of mildew - but this time I was able to pinpoint the origin to the driver's side
windows where I noticed the door seal below the inside panel was hanging
because the suspension holes in the rubber were ripped and the clips at the
front of the panel on the driver's door were not fully fastened, possibly
allowing water to enter and causing the mildew smell. This was likely an
issue before I got the car and the seller tried to cover it up with air freshener.
The rest of the car (fingers crossed) seems ok, but the smell is a problem.
How can I a) get rid of the smell, and b) prevent a recurrence?