Did David dance before the Lord in the Temple? No, no record of that that I am aware of.. besides read the article. This has nothing whatsoever to do with dance.
For David's dancing check 2 Samuel 6 when the Ark was brought to Jerusalem. Lots of dancing there.
I don't believe any authority in any of the various Christian churches in the world has ever denied that Thomas' Christians were Christians. No doubt there are ceremonies (and some beliefs) with which they don't agree, but the fundamental legitimacy hasn't been attacked. If so, maybe you can dig it up for us.