I've never seen a Made in USA Nishiki (nor any other bike in decades) but that's beside the point.
To the point: One does not have to just throw a bike into a truck/car, and there's no need to pile stuff on top of it. Using just a modicum of care will save much in the long run. All the other issues you mention - miles, hills, rain, mud, etc. are met by many other riders and bikes. The key is regular maintenance, rather than allowing things to deteriorate for "a couple of months" or more. Anything you ignore will only get worse and more expensive, especially with the drive train, where one part can directly affect others.
Rather than fiddling with parts learn correct procedures for maintenance and repair and apply them regularly. A bike obeys the rules of physics and troubleshooting it is a logical process. There is no shortcut laundry list of what you should do with $50 per month. Start with Sheldonbrown.com, parktool.com/blog and Google to learn how to address each issue.
Finally, road bike bars evolved because they give the most efficient riding position and a variety of options. They also are available in wider widths than standard, so don't abandon them without considering other options.
Last edited by cny-bikeman; 07-08-13 at 01:29 PM.