Is there any truth to my impression that if someone doesn't attend a leading seminary you can't really progress in scholarship? Does a person have to have a doctorate to be considered a scholar?
You raise some good questions about the nature of true scholarship. On the one hand, true scholarship does not necessarily mean going to the right schools. A person can be a decent scholar even without much formal education! But, at the same time, it's difficult to get through a tough, well-known school if one is a bad scholar. What the good schools show is a certain pedigree, a certain quality of education, training, method, thinking, etc., that is usually missing in the lesser schools. At the same time, if one goes to a mediocre school there is still usually some decent scholar there. I went to a mediocre undergraduate school (that is now a much better school). But I latched onto one scholar who guided a lot of my thinking. It sounds like you've done something similar. As for getting a PhD, this is more a modern notion, though the Germans have followed it for some time. The British have not. In England, up until the last few decades, a PhD was often looked down upon: If you had to earn your PhD to prove your scholarly worth, you were a second-class scholar! Some of the great scholars in the middle part of the 20th century, and even through today, never earned their PhDs: F. F. Bruce (MA), C. F. D. Moule (MA), and Kenneth Kitchen (BA)--the world's leading Egyptologist!--come to mind.
On the other hand, if someone is reticent to get a PhD but wants to be a good scholar, one has to wonder what the thinking is. Is it the cost and inconvenience? Is it the time involved? Is it that the person is afraid to think, to be challenged to really wrestle with the issues? If so, especially for Christian scholarship, I would have some questions about whether avoiding a PhD is the right approach. For one thing, Jesus never put a premium on ignorance and we dishonor him if we try to "get by" on less education. Sometimes a person doesn't want to be taken out of circulation, doesn't want to stop serving God in some ministry. But this is to think that ministry is only in relation to people. Fundamentally, ministry is what we do toward God. We serve him. To spend time in theological education is to love God with one's mind--if it's done right. And that means to minister to God.
Secondly, I think that the preparation of the mind for a life of academic service to God needs to be handled carefully. It is best handled in a community of likeminded individuals, learning and being challenged by multiple scholars, in the context of excellent primary and secondary resources. This can't be done when one avoids a PhD IF that person is also away from a community of thinkers or lacks resources.
Finally, if a person is interested in teaching on a college level, a PhD is a sine qua non. Few schools will accept a person on faculty nowadays without a PhD.
One last comment: those scholars who did not get the best education often do a much better job in their academic careers precisely because they feel the stigma of their educational background. Conversely, often those who went to the very best schools end up not producing very much because of various reasons. They may not feel like they have to prove themselves or they are even afraid to get peer-reviewed for their work.
I trust that these points may help you in your thinking as you strive to serve Jesus Christ.