Illinois law regarding residential landlords and tenants is highly specific depending on your location. Some places, such as Chicago, Urbana, and Evanston, have very comprehensive landlord-tenant ordinances that touch on almost every aspect of the landlord-tenant relationship. Other locals (usually rural areas) do not have relevant ordinances and reply on Illinois state law and common law. This answer takes into account Illinois state statutory and common law, and before you make a decision you should check to make sure Calumet City does not have a specific landlord-tenant ordinance.
1. Generally speaking, a landlord's ability to evict a tenant for non-payment of rent is almost exclusively the domain of the written lease absent a constitutional or statutory restriction. The best advice would be to have a lawyer review the lease to determine if such a situation was contemplated and what the lease had to say about it. The common law rule is that non-payment of rent, for whatever reason, could be grounds for eviction.
2. Security deposits in Illinois are controlled by state statutes and local ordinances. It is important to remember (and many, many landlords seem to forget) that a security deposit is a deposit -- it is the tenant's property and may only be properly be used for repairs and other items as directed in the lease. Many form leases contemplate that the security deposit cannot be used for rent payments at all. Depending on how your lease is written (again - consult a good landlord-tenant lawyer in your area) it is likely that the landlord can only use the rent for damages or other collateral matters to the property. However, the general rule is that the length of time a tenant resides on the premises is irrelevant to the ability of a landlord to use the security deposit for damages.
3. The general rule in Illinois is that a tenant is responsible for the remaining rent on the lease if he or she moves out early. This is limited by the landlord's duty to reasonably mitigate damages by taking steps to attempt to re-let the premises. However, a tenant could raise several affirmative defenses to a legal action by the landlord to collect the remaining rent based on a warranty of habitability theory, contract defenses, equitable defenses, or other matters. This is heavily fact-intensive and a good attorney should be consulted.
Please note that I am licensed in your state. This answer is general information that should not be relied on as legal advice. Always seek the advice of a licensed attorney in your jurisdiction before proceeding. This answer also can not be used to avoid income tax liabilities and should not be relied on as tax advice.