The first part isn’t analysis, its all assertions without proof.
On the second part, most of the train videos show T72A/B’s and older version MSTA SP guns. One such video shows @20 T72B3’s.
This on its own proves nothing. This spate of “train videos” were released by Russian sources as propaganda.
On the second, also, US satellite recon and signals intelligence would know exactly where any massive Russian concentration is, or will be, in realtime. This is obviously being fed to the Ukrainians, and they would be behaving accordingly. They dont seem to be worrying about some armored fist in driving range.
Etc.