Dragons vs. Balrogs?

[Kuruharan]

The Ents are the 'kelvar' spoken of in Of Aule and Yavanna, in the '77.

Yes, but what were they?

And it is much more likely than Goldberry being Yavanna.

The evidence for Goldberry being Yavanna is very sketchy (and rather far fetched in my opinion). There is no explicit statement regarding her true nature.
Dragons are at least explicitly spoken of in the text as having spirits in them.

..., and [Glaurung] spoke by the evil spirit within him.

I do not believe that the spirit of any mere beast (assuming that beasts have spirits) would be capable of the actions of the dragons that are described to us.

and thus bound in life and death to their hroar.

But didn't we just establish that Balrogs were also bound to their bodies?

His offspring, though not full Maiar, would've been mighty beings, and probably sentient.

So do these later dragons only have part of a spirit, or how does that work if the bodies of new dragons were not inhabited by Maiar spirits?