Yes you can cut off a finger or hand but I would never allow irrational fear to prevent me from using it.

Even when a PSA is in place, generally there is nothing to prevent an agent from soliciting backup offers (other LOI's) in case you do not close for whatever reason.The seller / agent seem to want to move forward with you but do not want to 'tie up' the property until they are more confident that you will close.

As soon as we move to an a place we think we would live in for the long run, then we would put down roots until the real estate overtakes our regular income.My question is this!

To install them, you do drill right through the asphalt shingles, but any reputable installer also installs high quality metal flashing over every penetration to prevent leaking.

Even if you could, why lock someone's stuff in the property and prevent them from getting their belongings?

It doesn't prevent anyone from suing you if a tenant falls through a hole in the kitchen floor and the oven topples over and hits them on the head.

A certified letter saying "no" or "OK, but" will prevent this. 

This will prevent anyone from changing their mind.

This saves me and staff time from driving multiple times to properties, it prevents wasting time in the event of a no-show, and I found it creates a sense of urgency in potential tenants as when they come they see other folks looking at the unit. 

Yes, and I was recently told to leave 12" of space between the house and mulch to prevent termites.