Why? We've got that, too.

I think it should be accepted, though adding "это" sounds better for my Russian ear for this sentence. :)

It worked for me.

Only if you want to say it in a way like 'Dad, he is a man'. If you want convey the fact that dad is a man you usually use 'Папа мужчина'.

Neither was ‘nahoditsya’....

Good question. I would have expected папа to be "dad" with a more formal word for "father". ( like in French, papa vs père )

I belive it's because the russian equivalent, "является," for "is", is not required to be in a sentence. It can be replaced with the dash, "это," or a space. Feel free to correct me if I am wrong.

That's the way of translating "is a"

Because есть means eats. That would be father eats men.

It's not incorrect, but it would sound awkward. "Быть"(to be) nowadays is usually omitted in the present tense.

Она была здесь.(She was here) Она здесь.(She is here) Она будет здесь.(She will be here)

Карандаш здесь.(The pencil is here) Здесь есть карандаш.(There is a pencil here)

It could be used in formal speech, in some cases when omission would change the meaning of the sentence, to spice up informal speech(not randomly, you have to know if it works).

I believe that would change the meaning to "The father is this man".

You might find this helpful https://www.duolingo.com/comment/11536858

Try olimo's guide for an explanation: https://www.duolingo.com/comment/11536858