"He is singing."
Does "kantas" cover both "is singing" and "sings"? Are there other present forms in english that it covers?
"kantas" is the (only) present tense in Esperanto, so it covers both "is singing" and "sings". What are the other present forms you are thinking about?
Also, you could actually say "estas kantanta" for "is singing", but I think people would usually just say "kantas".
(Edit: fixed typo, I’m confusing with Portuguese :D)
I think a more accurate translation for He is singing is Li estas kantanta, however it also accepts Li kantas.
No, but there is participles, which sometimes remember continuous tenses in some way. But you don't need participles most of the time. Participles are useful when you want to add extra precision to a sentence.
However, another possible translation is "li estas kantante", isn't it? Dankon!