I find it incongruous for you to use Early Church Fathers to support your interpretations since the debate between the Early Church Fathers was not whether the Earth was created over billions of years versus six days, but whether it was created in 6 days (as indicated in the plain reading of the text) or six nanoseconds (as suggested in the Apocrypha). Augustine's error was in attempting to compromise between scripture and apocrypha. OEC's on the other hand are attempting to find a compromise between natural science and scripture.
Historically the Church as well as the Jewish scholarly tradition have always argued for the 6 day creation. Clearly the debate up through Calvin and the Westminster Confession was always whether it took 6 days or 6 nanoseconds and only recently (the last 200 years) has any serious Christian scholar suggested that it took God 6 billion years to complete his work.
What I fail to see is why you believe in the antiquity of the earth yet claim you do not believe in evolution. If you are going to buy into the science which suggests that it would have been impossible for God to create the universe as suggested by the literal reading of Genesis, then why on earth don't you buy into the theistic evolutionary position that God used evolution as the process for making life on the earth? You are putting science on an equal footing with scripture anyway, so why not just accept what scientists say about evolution?
P-M, it is possible that OEC's believe that God did create instantaneously, but in between those "days" there were vast periods of time. They would believe in "ex nihilo" but they would not believe in gradual evolution over time.
In that case, the only difference between their view and the traditional one week view would be the amount of time between each day. We would have the days immediately succeeding one another. They might not.
I imagine that truthfinder9 can correct me if I'm wrong about OECs.