OEC's believe that Darwinian evolution did NOT occur, that the evidence for antiquity of the universe is overwhelming, old age is not equivelent to evolution (that's a myth created by evolutionists who appeal to time to solve their problems and by young-earthers who have bought into the evolutionist's claim that antiquity is a evolution "proof"), the literal Adam, the special creation of man and animal life, that a literal and consistent interpretation of the Bible requires OECism. Etc.
Thiestic evolutionists (TE) believe God created the universe and let it go and allowed evolution to take control. Some TEs believe God occasionally interacted with the universe after letting it go, some do not. Some TEs believe there are signs of design in the universe (like OECs & YECs do), others do not.
There are actually a variety of creation views that don't support evolution (however, some YEC theories on animal speciation after the ark actually require some very fast evolutionary processes!), here are the four main ones:
Four Views of the Biblical Creation Account
These articles compare YECism and OECism:
Ten Major Similarities Between Calendar-Day and Day-Age Creationists
Ten Major Differences Between Calendar-Day and Day-Age Creationists
It's really like any other Christian topic, there are various theories considered acceptable by orthodox Christianity, but most people are familar with what they grew up with.
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?