I was at Petra about a month ago -- I agree completely with what TravelingStudent re time at Petra. 4.5 hours will make for a pretty rushed visit. It's very unlikely that you'll make it to the monastery and you'll be limited to getting the highlights of the rest... that wouldn't have been enough for me, but it all depends on how excited you are about Petra. If it were me I'd probably sacrifice Wadi Rum and plan on doing the monastery the following morning, and if you're able, maybe push back the arrival into Tel Aviv a few hours.