To answer your first question, you would still say "they are", not "they is".
While I think the they/them pronouns thing is silly, there are cases where it's acceptable to use they/them in a singular fashion in English.
For example, I often have a managers' meeting at work where I give feedback on what team members have told me, but I want to keep each person anonymous. So I might say: "
One of my team members said they felt team morale was low". I deliberately don't give the gender of the team member to ensure it's harder to work out who I'm talking about.
I suppose I could say "
One of my team members said he or she felt team morale was low", but to be honest it sounds more awkward, probably because it draws attention to the fact I'm trying to anonymise the feedback. In that context, "they" is more commonly used and sounds more natural.
To answer your second question, you don't really use "it" or "its" for a person in English because it comes across as rude, due to the dehumanising nature of the word. People who choose to use "it" or "its" in that way almost always mean it as an insult -- e.g. "
tell it I'm not speaking to it!".
Here endeth the grammar lesson.