Without copying the entire email, I thought I would chime in on your problems. While I have never taught in the elementary schools, I have worked with my colleagues who do. Since each state is autonomous when it comes to education, you may want to check with your state education department for any "guidelines" or laws that you are seeking. I would bet that the only thing you could find that looks "official" would be the minutes per student, and nothing about facilities, supplies, time for lunch (we have 26 minutes for example), etc. What IS negotiable in the time "area" is done through the unions, unless you are at a Charter or Private School. (then all bets are off).
Here are my suggestions:
Do all that you humanly can, but if you can't do something i.e. hang bulletin boards, display work, etc., loudly and professionaly say "I don't have any time" and explain your situation concisely. Either "they" will stop asking or wondering, or something will change.
Get involved in your union, know your representatives, and take any extra time you may have to be an advocate for others who also have problems. Come up with solutions to your problem and problems of others. Make everything a team effort.
Volunteer to be on as many committees with other colleagues. (I know you don't have time, but one of the ways I have garnered respect with others in the building is that they have served on committees with me, or I have helped them in a problem they might have). People from all departments know me, have worked with me in and out of the art context, and when I need a favor I have no problems finding volunteers to help me out. In education, "bartering" for services is where the strength lies, not in administration. Those of us in the trenches have to make education work, we can not rely on the administration in any way to do that for us. So, for example if you are asked to move children from one place to another and then pick up their lunches, say "I will gladly do this for you, and the next time I need help I expect you will be there for me, as I am for you". And then call them on it. If they can't or won't help you when you need it, then the next time they ask you are able to say "I'm sorry, but I can't". As
k for help from these volunteers for hanging work, for example, or whatever else you might need.
Join the PTA. The "T" stands for teachers. You need to be an advocate for your services for the school. Don't make it a "complaining" session, but make it a positive experience, where you ask for parent volunteers to help you do what you need to get done between classes but don't have time to do. Again, hanging work, matting work, even gathering materials. I had parents volunteer to help me one of the years I was yearbook advisor, they proofread for me. You need to set guidelines though for any volunteers.
I have worked through all kinds of diversity over the years. Even now after 33 years, I have no supply closet and everything is in boxes scattered around the room. Hey! if it doesn't bother 'them' it certainly doesn't bother 'me'. I have also worked in a substandard sized room where between the kids and the tables I couldn't get 'around' to all of the tables. Over the years we have taught 6 classes while every other department taught 5 classes (we have gotten compensated in the contract just recently). I don't worry about it, because apparently no one else does. I just teach, love the kids, and move on.
I sense an urgency and anger in your post. It will eat you up if you are not careful.