Fold mountains
All of what you said seems reasonable to me except the erosion of the
Applachians. The modern Applachian chain is very clearly a folded structure.
The Easternmost fold — Blue Mountain — stretches for many hundreds of
kilometers broken only by the occasional water gap. To further complicate
things, one of those water gaps — the New River gorge — runs backwards with
the New River originating East of the Applachians and draining into the
Mississippi basin.
The other question would be when the modern Taconic mountains were emplaced.
They are mostly Cambrian age seafloor slates with a few carbonates. They
appear to have come from the East. After the ancient taconics of your model
eroded?