Whenever I see miners having similar doubts to the ones you have presented I always try to point them in a more simplistic direction. When people are worried about maximizing their earnings that is normally when they start making strange mistakes. Too many people try to "optimize" their earnings, without realizing that there are good days, bad days and the card you are running is extremely old. It is incredible that those series of cards are still able to output more than $1 a day.

I would suggest using NiceHash, not because I particularly love them, but they instantly convert your mined coin into BTC so you don't have to worry about conversion yourself. Plus, they benchmark your cards for multiple algorithms and always keep you on the most profitable one so you don't need to worry about these questions.