You can also see the distance for each flight segment (including the nonstop distance for direct flights, as DL uses) by clicking on the flight number on your search results.

To calculate MQDs, add the fare and any carrier imposed fees (such as fuel surcharges) but do not add any government imposed fees and taxes (such as customs and immigration fees, airport improvement fees, excise tax, VAT, sales tax, etc.) as indicated on your receipt, and don't forget to convert the amount to USA dollars.