Personally, I think your commute would be easier and more fun with regular pedals. But if you must, keep the tension low until you're totally comfortable and can clip/unclip instinctively, without thinking about it. Just because you can clip/unclip during test rides doesn't mean you can do that equally well in traffic during real commute ride when your senses are busy with gazillion of things around you.

Then you can tighten them up gradually and make further adjustments. You should be equally comfortable unclipping with both legs as life will not always let you do things the way you prefer so you should be able to get either foot out quickly.

As far as cleat position. Unless you have a bike trainer, stop by a bike shop. They can help you with finding the right position while you spin on a trainer. Otherwise it's a trial and error process. Getting the cleat position wrong might cause joint problems, etc.