Lots of questions - I'll talk about just a few:
Distance - You can start off doing a partial bike commute (driving part way and cycling the rest), or commuting only some days until you get stronger. There are plenty of ways to ease into the commute.
Price - Tell your wife that $1000 for a commuter bike will save 4 times that in auto costs in a year.
Safety - I always say that commuting can be safer than weekend riding because it is so regular that the drivers get to know you and expect to see you on the road.
There are riding methods that will improve you safety and help control how the drivers react to you. There is a GREAT cycling course sponsored by the
League of American Bicyclists that I think should be mandatory for adult cyclists. I am amazed how much I learned and how much more I can control how I am treated on the road.