DME is not a fun airport to hang out in for 8 hours, I'd consider hotel or even taking the train into Moscow.
Before customs there is Paprika which has not bad Indian/Eastern food. I do think the S7 lounge is also accessable for Priority Pass if you have one and are not travelling business/elite/etc. There is also a spa which I have never been to. Thai-Spa salon “7 Krasok in Domodedovo Airport.
Of course you can always drink.
Bege