I write: the sheep is eating.
DL corrects me and says it was meant to be: "the sheep ARE eating"... However this sentence translation feels awkward. Since my sentence was still present tense i feel like i was right...
No. "schapen" is plural. It's the equivalent of saying "They eat" - "Zij eten", not "he eats" - "hij eet". If there was just one sheep it would be "het schaap eet", but there's more than one sheep, so it's "de schapen eten".
No, the plural of sheep is sheep. There's no separate plural form for some animal nouns, like sheep, deer, moose and fish. (Fishes can be correct in some circumstances, but generally fish is the correct plural.)