My battery was stolen while the TT was at a storage facility so removing it is a good idea.
Definetly cover the tires to protect them from the sun. Get the vinyl wheel covers sold by CW or similar. Plastic bags aren't the right thing for the job.
Get the bigger patio stones or better yet make some simple forms and use quickkrete from Lowes or Home deopot to make pads for your tires.
Consider covering it with a cover like ADCO - look them up on campingworld.com. Especially if you are close to the ocean. It will keep your TT clean and protected. Send me a PM if you want to talk about covering - some of the folks on here seem to be against it.
Propane tanks - up to you. I don't take mine off and have no issues, but consider your own situation and do what feels safe to you. Just keep your eye on it.
Don't forget to get some kind of hitch lock and maybe run some chain through your wheels.
Make sure your insurance will cover it where you plan on parking it.
Good for you that you have a free place to store it - beats paying for storage!
