Unfortunately, this tree looks like it is finished, I'm sorry to say. Most of the canopy appears to be dead and there is not anything you can do to help it recover at this point. We know how difficult it is to lose a mature tree like this. You should contact a licensed tree specialist or certified arborist to have the tree taken down safely. 

Go to the "additional resources" links at the bottom of this page to find a licensed tree expert.
https://extension.umd.edu/resource/how-do-you-decide-when-remove-tree

If you are interested in planting a replacement tree, some counties in Maryland offer rebates for tree planting. Check with your county government's office. The Maryland Department of Natural Resources also has a rebate program to support tree planting. https://dnr.maryland.gov/forests/pages/marylandersplanttrees/introduction.aspx

Christa