IIRC, DC was kept separate in order to prevent the host state from pressuring the federal government. It was certainly a real risk in the early days of the nation—Virginia would have had no qualms about directly harassing representatives of non-slave states, much less merely standing aside while bands of thugs did the dirty work.
The balance of power between federal and state governments has shifted since then, and provided DC can maintain its own police force I don't see huge risks in lumping it in with Virginia or Maryland now.
The current bill is unConstitutional. The proper way to go about this is with a Constitutional amendment.
But DC is such a tiny area, with a small population and essentially no industry—nothing productive, anyway—that it is a joke to call it a state and give it a couple of senators just like New York.
I'd go with maintaining federal jurisdiction for DC law enforcement and making it a part of Maryland or Virginia (flip a coin—loser gets it?) for all other purposes.