First, we'd need to discount the mainline Protestants for whom the sacrament is pretty much meaningless other than as a comfortable habit.
The Baptists would be the largest of the symbolic crowd, and they've had a large influence on the large 'E' Evangleicals. On the other hand, there has been a lot of recent discussion as to how large the Southern Baptists really are - certainly far smaller than their claimed numbers.
The Lutherans and Reformed are discussed above - and there are a lot of Lutherans in the country.
So I'm not sure I'd concede the 'prevalent' at this point.
2. I don't see much left to debate there.
I have to post and run - I'll get back for the other 2 later.
Well, Anglicanism doesn't really have a fixed teaching on the Eucharist - some certainly teach the symbolic understanding, others don't. So, we can add some of them to the total. And, although I think we'll get into this when you come back, from my vantage point, I'd argue Calvinism teaches the symbolic understanding - however, like I said, that was point 3, so we'll work on that in a bit.
I don't know enough about Presbyterians or Methodists to really have an opinion, but I'd guess they have a more symbolic understanding. And I certainly think "Purpose Driven" groups have a symbolic understanding. Anyway, I look forward to continuing this conversation.