An 11-year old who wants stories at bed-time seems outside of the norm, in my opinion. It sounds like your SS might be using this as a tactic to get his dad to stay with him a bit longer. Nonetheless, I don't think it is unreasonable to agree a bed-time for your SD while he is staying with you both.
Talk to your husband. Especially about the rudeness, disrespect, entitlement, ungratefulness. Give specific examples. Your SD needs to understand that you are not an option. You are in his dad's life and therefore you are in his life as well. You are not an afterthought. When SD is at your house, he is part of your family, not the other way around. In addition, it is also your house with your DH and SD is not allowed to speak to you disrespectfully. If he has a grievance, he should be given room to air it.
You also need to negotiate a compromise with your DH about his and his son's bed-time. I don't think it is unreasonable for a wife to want her husband to go to bed with her at the same time. I also don't think it is unreasonable to want to spend some quality time with your husband while your SD is staying with you. It doesn't matter that you've been under the same roof for 11+ days. It is your house as well and you shouldn't have to make yourself scarce for 3 days every two weeks in your own house for the next 7+ years.
And this is not a baby SS, he's 11-years old for goodness' sake. Your DH does not need to be at his beck and call for everything. There will be times when your SD needs to figure things out on his own. And there's no point in your being there if dad wanted to give up his entire life for his kid(s), leaving no room for his SO.
Your SD needs to get used to you being there. But you do also need to find a compromise with your DH about spending some quality time together, even when it's during SD's visits, e.g., you can cook together while SD watches cartoons. You might also have to accept that some weekends won't go as planned. But some weekends will go perfectly. I suggest finding things that you can do while your SD is with your DH, so that you're not "waiting," and therefore stewing, for your DH to be free.
I also think that you should try to find some common interests with your SD. This will go a lot easier if the two of you can connect and have a good relationship separately from your husband. You may/may not want to be another parental figure, but since you will see a lot of him, why not be a good influence and another source of support in his life?
I wish you an abundance of patience and strength.