You might need to check your math. In order for a 2% fee to be a net loss compared to 100 less sol/s your setup must output over 4900 sol/s, which is outright impossible even if you have five 1080 Tis.

More realistically, I'd expect each of your five 1070s to work at around 480 sol/s. That's 5×480=2400 sol/s, or 2400+100=2500 sol/s with bminer. Deducting 2% dev fee, that's 2500×0.98=2450, which is 50 sol/s more than EWBF.