Just walk in and change the lighting. Your best bet is to get a timer......your plants will go nuts if you change things around sort of willy-nilly......even 10 extra minutes with lighting can mess them up..... your 12/12/ times should be EXACT and your place should be completely lightproof but with good air flow etc.....otherwise hermies and all sorts of cool things could happen.

Yep, just a normal dehumidifier if your rh is over 50% (I like mine in the 30's......)

And just an aside......flower as many as you can in your space. You're going to spend several months on this project.......go for as much gusto as possible for your work, money and time.