Roommate in arrears and landlord threatening to not renew the lease. Options?

Hi all. I live in a "4-bedroom" apartment. One of the "bedrooms" does not have any windows and we've had trouble with having a roommate stick around in that room. One roomie stayed this entire past year, but as it turned out, she had not paid her rent in 10 months. She owes about $10,000 in arrears and outright told us she had $200 in her bank account only AND knew the room was illegal so she can't and won't pay. Landlord told us if she does not pay, he will not renew the lease come August 1st.

He has not officially told us to move out/ nor served us anything. Not just that, but he has falsely advertised the house as a 4-bedroom apartment when it really is just a 3-bedroom apartment. He also has all the windows in the apartment locked with steel/metal grills (probably for safety from outsiders), but that means we have no fire exit at all. For more context, 2 roommates have lived here for 2-years now.

What are our options? 3 of us want to live here, and let the fourth one who is in default leave, she is ready to leave as well. But what are our legal options at staying?