is there a word in arabic for 'is'?

Yes we have that word يكون But since we conjugate the adjective based on the subject and the single and plural, we drop it, it us not necessary.

Sam is generous You can say سام كريم(most used) Or سام يكون كريما(almost not used)

Sam and George are generous سام وجورج كريمان Or سام وجورج يكونان كريمين

Reem us generous (reem is famle) ريم كريمة Or رييم تكون كريمة

In the all above first sentences, you can see the adjective changes corresponding to the subject So it us nit necessary to use "يكون" at all

Are the rules for deflecting the nouns (-un/-u in the nominative case etc.) extended to names?

I heard that Arabic is a VSO language. Then shouldn't the sentence be the other way around (kariim saam instead of saam kariim)?