Touche-although it sounds like you already have a decent bike!
Get on of those DIY 99 dollar divorce kits!
On a more serious note, I would imagine that your wife might be expressing some insecurity about her own health and weight, etc... vicariously through her snide comments on you actually doing something about it. My girlfriend did something similar when I started getting serious about eating and living well, now she is coming back around. I am trying to see if I can get her on a road bike, don't know how well that will work but it is worth a shot.
Speaking of paperwork, anyone want to write my paper for me on Glenn Loury's "Anatomy of Racial Inequality"? Because I really would like to go to bed!