In Chicago, you can only break a lease if the unit is not fit for habitation. The remedy for lack of A/C would be a small reduction in rent. The remedy for a broken toilet would be for you to call a plumber, and send the receipt in with your next rent check, less the cost of the plumber. Are the smoke alarms hardwired? Do they go off for no reason, or are they simply sensitive?
Mold could be a reason to break a lease, although if I were a tenant I'd want a doctor's letter stating that mold has aggravated some condition and that I can no longer reside at the house.
Like someone else said, document everything. Send the landlord a certified letter stating 1) how much you will be reducing the rent because of a lack of A/C, 2) when you will be calling a plumber to fix the toilet and that you will be deducting the repair from the rent, and 3) whatever you want to do about the mold and smoke alarms.
Document, document, document with copies, certified letters, and pics.