Couple random thoughts:

It's been a while since I did any exegetical work using the Greek, but I took a look at 1 Corinthians 14 to see if anything would come back to me . I think the language used there supports your assertion that instruction was being given about appropriate behavior in worship services, although not just because of the word "but."

I think Petersen got the idea of the Greek right in his translation: "The one who prays using a private "prayer language" certainly gets a lot out of it, but proclaiming God's truth to the church in its common language brings the whole church into growth and strength." (MSG)

Question: Where did you get this? "In fact, in the Corinthian church, those that wanted the "prestige" of a tongue talker would speak glossolalia, a practice carried over from many of the ancient false religions back then." I'd like to see some resources about the place of glossolalia in the religious practices of that part of the world in that time. Not saying you're wrong, but such a strong statement should have some good backing.

My current pastor (I'm now in a Methodist church) pointed out a very different possible interpretation of the story of Pentecost: The miracle was not in the speaking, it was in the HEARING. The people present had to HEAR in their own languages. That doesn't have to mean--if you are assuming it was a truly supernatural occurrence--that the people were speaking the languages they heard.