How much ballet is safe to practice at home?

I have a Nutcracker audition coming up in about two months. I will be doing some ballet cles this summer, but I really want to improve by working at home, too. My balance is HORRIBLE. Would it be safe to practice balancing in different positions (pe, coupe, develope, etc.) at home or should I try to ask for help after cl or something when the teacher can help me? Also, I would like to do a quick barre every day. Is that okay to try at home? And I would like to keep working on my extenstion this summer. It's actually really good, but I want to get it even better. Is it okay to do that? Thanks!