Traffic on Sunday morning will be light. Actually you can explore the city for a few hours if you want to.
I'm not sure if there is an official taxi stand in SVO (there is one in DME), but the airport's web site has rates for the approved taxi companies (company?) and the fare to DME is 3400/4100 roubles ($57/$68) depending on car class. Slightly on the higher side IMHO, but I can't call it a rip-off. Checking what Uber offers may be a good idea
Arriving at DME 2 hours before your flight is recommended, though for a domestic flight 75-90 minutes will probably also be OK even with luggage to check.