Are my thoughts wrong aka how to deal with selfish siblings

I feel some guilt over a decision I made, and need some outside perception on my choice.

Back story, (and it could get long) my 3 siblings and I have never been close, for various reasons but we have maintained a civil relationship.  I always maintained contact and connection even though I was the one responsible (fully, 100%) for our mother during her last ten years, with no help from any of them (emotionally, financially, physically).  One lives in the same town as I do, two others in bordering states (within a 4 hour drive).  I  have always acknowledged their birthdays, anniversaries, etc, with a card and gifts for their kids.  I have driven to the other states for major events, (first proms, sports events, weddings, baby showers etc). My one nephew has 3 kids now and each child gets a big birthday party that I attend with a gift each year.  One niece has 2 kids, and I drove out of state for the baby shower, and the 1st birthday party.

I have a daughter who attended grad school in Chicago and my sister, who lives 20 minutes outside the city, couldn't be bothered to go to her graduation.  In fact, not once in the 4 years she lived there, was my daughter invited to her home for a day. None of my siblings went to her wedding in Chicago.  My DD now lives in NYC, and with my one grandchild.  She comes home for a long weekend or week twice a year.  For last 7 visits, my brother here in town, and my SIL have not seen her,and my grandson (despite my invitation). The out of state siblings have never seen my 4 1/2 year GS. None of them have acknowledged her birthday since she was 16, and never any gift for my grandson.  My sister said she would be in state for their visit this summer and would come visit.  She, of course, didn't.

In January I had a major heart attack and quad bypass, and several complications after.  I was hospitalized for 37 days, home for a week, then back in hospital for a week for complications. My local brother came to see me twice.  My SIL called once. (Although when she had knee surgery I took her to therapy every day for 6 weeks.)  While I was recuperating at home, no phone calls, visits, no offer to drive me to Dr. etc.  It was my friends that took care of me (one who was undergoing chemo, one who flew up from FL, stayed with me, then took me to FL for a week, then flew me back, and one who was with me every day in the hospital and after, and who cleaned my house, and changed my sheets and chauffeured me everyplace for the 2 months I could not drive.  I am so lucky to have these warriors in my life.

My sister called twice, but although her in-laws live an hour away, and she was in state several times, didn't detour to visit me.  She now has a vacation home in my state, and she is there every weekend this summer, and has never detoured to visit me.   I did go to her birthday party at her vacation home early in the summer.  (Although my first thought was not to.  You know make the same effort to see her, that she made to see me).  It exhausted me.  I am only running at 50% yet. And despite her lip service, I have not heard from her since.

So I made the decision to just back off on the efforts to maintain contact with my siblings.  My first action on this was to skip the nephews one child's birthday party.  I got a phone call from my SIL asking why I neglected to show up for the birthday party and should she stop by to pick up the gift (I know, shocking isn't it?).  I was at a Dr Appt, and told her I would call back.  Do I keep the peace and say, that I am still on limited activity ( which I am, I can only handle one thing a day), or do I tell her, I am tired of being stepped on?  Do I maintain the middle child peacemaker role, or do I say  'I am done with everyone's selfishness'.  

As I read this over, it sounds like a pity party, but really the question is 'Should I just step away from my siblings' or should I just tip toe around the issue, that I feel that they have hurt, disappointed and insulted me with their self absorption. 

And for the record, they are all retired, as are their spouses and all their kids are adults. I still work part-time . And just to compare, I was widowed at 31, and raised my daughter alone, and of the 7 grandkids between us, only my DD has a College degree, and Masters.  So I rather think think my DD should be acknowledged in some way.  And that sounds petty too, but I think it affects my thought on this matter.

So  what say the wise peas?