Re #1, get some Wag Bags these you carry out, but apparently have a chemical powder in them to prevent the stink. OR: Not sure if burying the waste is allowed there, but a good poop kit is easy to carry. Just need a trowel (Deuce of Spades for instance) and biodegradable TP and hand sanitizer.

#2 have your significant other stand guard. Could also bring a small silnylon tarp and have them hold it up, or you can tie it off to trees (or trekking poles). Check out these dual purpose poncho tarps: https://www.amazon.com/Ultimate-Arms-Gear-Waterproof-Military/dp/B01G2EXZSQ/ref=sr_1_37?keywords=silnylon%2Bponcho%2Btarp&qid=1671662005&sprefix=silnylon%2Btarp%2Bponcho%2Caps%2C152&sr=8-37&th=1&psc=1 I have one like it from aliexpress. I use it for wind deflection when I'm taking breaks on day hikes or backpacking.

#3 not sure I understand. If you have bad knees/hips like me then squatting is painful. I try to use the lean-against-a-tree/rock method wherever possible. A fallen tree can also be a nice place to sit with your butt hanging over. Though trees are likely not prevalent there. So not sure how to help with this one. I also sometimes use a rock if it is shaped right. Bring a 1.5' or so square piece of CCF foam. Makes a nice sit pad for breaks and for pooping. To use when pooping put it down on a fallen tree or rock and "sit" on it so your thighs are on it and butt is hanging in the wind -- so to speak.