When training for fat loss, you should always shoot for incomplete recovery, meaning that you must accumulate an oxygen debt from set to set.
Your breathing should stay hard and heavy for the whole workout. If you can talk normally during a fat-loss workout, you aren't training properly! So the rest intervals should be shorter, even with compound movements.
This depends on your level of conditioning and work capacity. Since the goal is incomplete recovery, get back to work before your breathing normalizes!
During a fat-loss program, you should feel out of breath and almost nauseous during the whole workout (the nausea is mainly due to the increase in lactate/lactic acid production).
You should rest anywhere from 15 to 60 seconds between your sets with a tendency toward gradually reducing the amount of rest you take.