Diluted ammonia. Have good ventilation.

Those need dynamite. They aren't worth the effort it would take. Remove everything that is detachable, and then buy a 55 gallon drum of BIN shellac to coat the rest. Then start over, installing new finish materials.

I agree, not sure those are worth salvaging. That being said, my mom was a heavy smoker and we once cleaned her furniture with a mixture of boiled linseed oil, turpentine, and vinegar using 4 XXXX steel wool.

Pull up the contact paper first. Second, is that nicotine or mold?