@jim 1968,
First of all, Welcome to A2K
My husband and I were the support for his elderly mother and my parents (Mom diagnosed with altzheimers at 58 and Dad hearth disease) mr. G'bags brother died in 87 and my brother didn't feel a need to help, but at least we had each other and our son to help with the responsibilities.
Please don't beat yourself up for trying to keep your parents happy. It's only you, and I'm sorry they don't understand that you are entitled to an independent life.
You wouldn't have posted if you thought this was normal, and if you want someone to tell you you are entitled to your feelings, I'm more than happy to tell you you are asking the right questions and no, you are not solely responsible for keeping them entertained.
Personally, I have found support groups too often depressing with no one offering real ideas mostly just bitching about how difficult it is. But don't rule them out, some can be wonderful. You should be talking to people who know what its like to deal with demanding parents.
The others are right about expanding your independence, and I think it might be a good idea to think about those other 15 relatives and reach out to one of them that you remember as nice, fun,or family when you were much younger. You really shouldn't ask for permission, just call someone who has tried reaching out to you. Don't talk about old family slights (thats between your parents and the others), you probably have several cousins who would love to hear fro you. They probably have a much better understanding of the situation than you realize.
The last thing in the world you should do is put your life on hold until your parents are gone. I'm not being flip, you are entitled to be as happy as you can be. You might not always have the luxury of flex time, and you can't jeopardize your future because you want to keep your mother mollified.
I hope you stick around because I think you will find folks who can be helpful.. This might only be virtual friendship right now, but I've been sharing things on this forum for many years and I've come to know many wise compassionate folks.
My only suggestion right now would be to use this forum as an extended family. Hopefully you will continue to seek out real life family relationships and develop a circle of friends.