Just a little tip for the future. Learned this from some autobody guys. Mix up a spray bottle with a little liquid dish soap and spray this on the floor and let it dry before you paint. When your done the overspray just rinses off.
Been using one of these for the past few years. The only moisture issues were when the air became warm and the stuff in the garage was still cold moisture would condense on it. Also dont run them on a very low setting they can put off a black soot that settles on everything.
I dont know what is recommended. On my neighbors garage they stopped the cut inside the garage. When the floor cracked it followed the cut line inside the garage till it got to the end of the cut it then went in multiple directions outside the door.