My take on it:
1~ if second set of sheets was 'dirty', I would wash them and bring them back to the guest. No need to purchase more.
2~ You provided non-plastic dinnerware; no need to purchase more.
3~ If the deck window needs more privacy, tell them you'll consider buying and installing a curtain and rod if you decide to provide that. Don't let them choose it or install it. You're paying for it, you get to choose 🙂 I wonder if it's a window that you could put a tension rod in place just inside the opening ? That way no screw holes are made.
The space comes as-is. That's the norm. It's your space to decorate as you wish. That's also normal.
I'm not sure how you would go about giving back money to them as it's all going through Air bnb. Keep all messages on the air bnb site for your records 🙂 You are not obligated to change your space to please every guest. Best wishes~