DC Taxes Witheld, Live in MD / Estimated Tax Penalty

I live in Maryland and work in DC, and realized I paid income taxes all year to DC.  I'm trying to figure out the best way to handle my Maryland filing through Turbotax:

 

  • Do I fill out a 502CR?  Turbotax says I can't enter credits based on income from working in DC.  
  • I'm being assessed a hefty estimated tax payment penalty with the information provided.  Do I avoid paying this by indicating I worked in another state (DC) in Turbotax? I was otherwise planning on completing a D-40B form to recieve a refund from DC. 

Help!