You have begun with the incorrect assumption that your bitcoin miner will hash at a constant percentage of the network hashing rate for 730 days. I fail to see the usefulness of your graphs.
It makes no such assumption. As long as the network hashrate is at or below the lines on the chart, at any point in time you could buy a miner and end up breaking even after 2 years, of course constrained by the listed assumptions and the curves themselves, nothing else. If your point is that after 2 years the network may exceed those lines, thats actually part of the point, but it requires either changing constraints or someone betting > 2 year.