Excellent work! I would only add that the ARVN lost after U.S. Forces pulled out ONLY because the United States Congress (under long democrat control at the time) cut off their funding! It is VERY hard to fight a war without resources!
Add to that the North waited until after Nixon resigned for its final offensive to the South. This was an offensive with conventional mechanized forces. It the North did so before Nixon resigned, Nixon would have turned the skies over Hanoi and Haiphong dark with B-52’s, using treaty violation as the reason. Linebacker would have been a nuisance raid in comparison.