Maybe not what you want to hear, but you asked for opinions... If I was still in grad school, in debt, working extra to make ends meet, I would quit the extra job and spend more time with my family and lower my budget on a bike. You don't need to spend upwards of $2,000 to get a more than adequate commuting bicycle. You cite making less than favorable decisions in the past, being "broke", having to work for the bike shop in order to get the employee discount, etc, etc. So if that's really true, I would go with something much cheaper but still usable. When I was a poor grad student I made due with a second hand bike I maintained by myself and it was just fine. Just my 2 cents.

P.S. If the beginning of your original post means your wife doesn't understand why you need to spend $2,000 on a commuter bicycle, she may have a point. Maybe she's noticed a pattern. I'm such a spoilsport, aren't I.