Ouch, I don't think there is an easy solution to your unique situation.
If your methods leave a small amount (1/2" deep +/-) of gas at the bottom for 1.5 years, it will turn to goo.
An empty steel tank in the temperature/humidity fluctuations of Chicago might result in condensation and rust. Could it be fogged somehow?
Maybe remove the tank, drain, and store in a controlled environment. Or,
The only thing I can think of is to get the tank nearly empty by siphoning. Then, fill it mostly full with stabilized fresh fuel to eliminate moisture condensation and oxidation. Then siphon/drain/refill once or twice over the next 18 months.
Be REAL careful not to blow yourself up! I'm interested to hear other opinions.
Google "long term car storage" for other issues to consider.
RE your original title, I read (but cannot now find) a good article at the Chevron site that tried to dispell the E-10 "myths" about reduced storage time. In a nutshell, it said that todays gas is even "better" refined than in the past and that PROPERLY stored fuel SHOULD be able to last 12 months. Just an opinion.