Nice post! Glad to have you as a witness on Steem.
Currently only about the top 50 Witnesses stand much chance of recouping their running costs.
I don't know what number you use. At the current prices, only 2-3 blocks a day could be enough to make a witness profitable. This in turn mean a lot more than only top 50 witnesses are profitable. I would encourage you to correct this information or correct me if I'm wrong.