Newbie vivarium help

My son got a baby beardie a while back and we had him in an old 10 gallon tank, obviously he outgrew it. I did some (not enough apparently) research, mostly on this site about building a viv for him. It's 4' x 3' x 2', nice size for him to run around in, three levels, etc. I used plywood for most of it, flooring is slate tile that is grouted. Unfortunately, I used some cedar that was laying around from rebuilding our decks this last fall as supports around the edges. I didn't know until I had it built that cedar is bad for beardies. However, I did coat the whole thing in polyurethane. We waited about a week before putting him in there. He was quite happy until I came home last night and his saw that his eyes were a little puffy and he was a little lethargic. A few questions. 1) Do I need to replace the cedar supports with some other types of wood? 2) Or, do I just need to let the polyurethane cure longer? I think it started off-gassing fumes once we added the heat. 3) Would leaving the heat lamp on help the polyurethane cure faster and prevent more off-gassing? TIA