Urgent landlord tenant question on breach of contract in Chicago, Illinois

I have a signed lease agreement coming up with a landlord this week. Today he tried to back out because he said he forgot the other tenet wanted to extend their lease, but they have no formal contract. I have already paid rent and deposit in full and on time, I have signed the lease, and I am flying to Chicago in the next few days for an August start. He insists I take my rent and deposit back, but I want to enforce the lease because there is no time to find new housing. He tried to delete the online rental portal but I have all the signed documents saved. This isn't legal, does anyone know my rights in Illinois? I am from out of state. Location: Illinois