OP, what I’m about to write may seem harsh, but I don’t mean it unkindly. It seems like your relationships with all of your children are a bit rocky. Hopefully, you can make some changes that will result in improvements.
First and foremost, you need to contact social services and arrange for any help you may need. Put yourself into a position where you don’t need to ask any of your children for help. The impression I get is that your DS feels he had to put his life on hold in order to be your carer. At this point, it doesn’t matter if you think this is true. If it felt that way to him, it will affect how he relates to you. You also need to find more happiness in your day to day life. Find hobbies you enjoy. Join a support group for people with your kind of health issues. Spend time with your sisters or friends.
I don’t know why your relationships with your other children are so distant. I think you need to seek counseling to help you figure out what went wrong. You need to be willing to be honest with yourself and do a lot of self reflection. You may need to ask them directly why they limit contact with you. Whatever you do, don’t argue with them about it. Listen to what they have to say. Sincerely apologize and work on your attitudes and behaviors that have caused the limited contact. Hopefully, if they see that you have worked on changing, they may be willing to have a closer relationship with you.
Next, apologize to DS for relying so heavily on him in the past and reassure him that you have made arrangements for your current and future needs, so now you can focus on just enjoying each other’s company. Also apologize to both him and his fiancé for how you have reacted about Mother’s Day. Stop looking at her family on social media and never try to make comparisons of your relationships again. Just like your individual relationships with each of your children is different, DS and DIL will have a different relationship with you than they do with her family.
You have come across as entitled concerning your relationship with your DS. You seem to be in competition with DIL and her family. You need to realize that DS made a lot of sacrifices to be your carer. Saying that you made sure he had a clean home and meals doesn’t equal him putting his life on hold (to a point) to be your carer. You need to understand that as a parent, it is our job to provide for our children and helping them to transition into being independent adults. This doesn’t entitle us to them becoming our carers. Acknowledge the sacrifices DS has made for you and let him know that you are doing everything in your power so he can focus on building his future family with DIL.
A big thing you seem to be doing right is understanding that your other children are busy with their own families. I applaud you for understanding that their primary focus needs to be their spouses and children. Please give DS that same understanding as he builds his family with DIL. Ask him to share his new boundaries with you and follow them. Not calling after 9pm unless it’s an emergency is a reasonable boundary. I think it would be lovely to try and set up a day near to holidays to celebrate with your children. Maybe the weekend before or after each holiday.