I've been doing some work on TSCO for a few weeks now and believe your write-up is fairly comprehensive and well done. I would suggest revisiting your competitive advantage section; I feel you could probably make a strong case here. Additionally management while management has made substantive improvments to working capital and inventory turnover, there are some weaknesses here (or upside depending on your view).
Overall, great company with room to run. However, I agree with you that at this valuation TSCO is difficult for a value focused investor.
I follow many companies. Tractor has the best management team of any. It also has the least competition. They are positioned for a long run of growth and most impressively bring great bottom line results with modest comps. These guys know how to provide value to customers and make money in the process. My number 1 pick. I had to laugh a year ago with the stock in the mid 30's when an outfit named Rice Volker identified Tractor as their favorite short in the retail space. I expect they have since fired the analyst who made a judgement without knowing management or the niche they operate in.