I am going to second what
@Olive Drab Green said as far as growth and re-veg goes. It's gonna look a bit funky and take a little while to bounce back but she'll get there. If you do decide to bump up the humidity though, keep an eye on the existing bud sites. The can get a little mold/rot from time to time, but that I've only seen on outdoor. Shouldn't have any issues in a cab.
I was thinking about your light leak/sealing issue though. You could buy a roll of .5cm weather stripping at the hardware store and run it along the edging where the doors meet the frame. Looks like you might be able to place it on the contact area where the doors come together but it might be a bit thick. Also, you could improve temp and humidity stability and other possible light leaks by sealing the inside edges with bathroom silicone after your paint has dried. Give it 24-48 hours to let the fumes to dissipate though. The new cab is rad though man. I dig that finish on it.