You're probably not going to get a firm straight forward answer, based on the complications of your situation. My answer is gong to be wishy-washy. I would continue to file as a MD resident, just for simplicity. That said, I'm also of the opinion that you are now a DC resident for tax purposes.
"and also maintain my rental property in MD". That sounds like you are renting out "My permanent home is in Maryland".
That helps in deciding the answer to your complicated situation; you are a DC resident. You no longer have a permanent home in MD, you have investment property in MD. Furthermore, in determining "tax home", a "temporary job assignment" is one that is expected to last less than 1 year, even when your intent is to return.
Your situation is further complicated by the reciprocity agreement between DC & MD.
