Killing the filibuster would be fairly easy. Granting Puerto Rico statehood would just require a majority vote in both houses and the President’s approval. Packing the Court is possible but it’s important to remember that even FDR failed at doing it.
Eliminating the Electoral College would require passing an Amendment most importantly getting 3/4ths of the states to ratify.
D.C. statehood has all kinds of Constitutional problems. The 23rd Amendment would have to be repealed as well as the parts of the Constitution that directs that the District be controlled by the Federal government.
The whole point of the District is that the Federal government could not be held hostage by a hostile state government. Reducing the official district to a few Federal buildings won’t work. State police waiting on the sidewalk ready to arrest government officials and employees the now 99% democrat state government doesn’t like.
According to Article III, Sec. 3, admitting a new state just requires Congress to approve—it doesn’t require Presidential approval. So Trump wouldn’t be able to stop it.
Once they pack the court with 4 new democrats, the court will rule however they want it to.
They do not care about the Constitution at all. They want to ter it down.