Im am sorry to hear how you feel, and that they are aware and are ignoring the situation. While I think it is a great idea to go off to a ballgame or other activity and treat yourself right. If you can do that and enjoy, that would be great.
I hear a lot of resentment about the situation, and rightfully so. You sound like a very good husband and father, one which many would be envious of.
It sounds as though your children are all grown and have not learned the transition of providing for themselves. Of course if they have not left the nest, they are around with a need much more frequently.
There comes a time in life when it is time to re-connect with our partner, (I dont think you mentioned grand kids yet) before the family grows.
I think we get into such patterns (normal life cycle), and during the child raising years, neglect our relationship with our partner sometimes. Especially those of us who did not have the best childhood and want to make it great for our children. Reality is that the children will eventually (hopefully-lol) go away and the parents are left alone. From my observations, mothers have a more difficult time with the empty nest and men may be more welcoming. It is normal for the kids to have their own relationships that take priority over family of origin.
Can you take a weekend away with just your wife and no interruptions and take the time for fun for just the two of you. Maybe even delegate what may need done while you are gone. I know that it can be difficult to ask for what we need, especially since sometimes we do not even know what it is ourselves. This might prove to not only be fun, but give you the opportunity to share what you are feeling with your wife.
Nobody wants to feel taken advantage of. My generation, most parents didnt provide cars. I have kids and know how different it is. With cell phones, car insurance, etc, even when they have their own apartments, its often cheaper on family plans. Those out of college, could you give them a notice that either they get their own, or you will give them a monthly statement of what they owe toward these bills and what day it is due. I know you are grateful that you are able to do this, but allowing them to provide for themselves will give them a sense of self sufficiency. (even though it may be initially unwelcome-better in long run for their own esteem)
I hope I am not sounding critical because that is not my intent. You have ptsd and health problems and need to take care of yourself and lower your stress. This is not worth your life, accidental or deliberate. Making such a change is very difficult, particularly when you are so tired and worn down from how things have been. There is life after children and as a woman, I can tell you that ofter the empty nest, we do have to re-group to find meaning in life. (my situation different) but still discouraging.
My sister and her husband had children from different marriages and did not see them much, mostly because my sister is not real nice to anyone. She complained a lot of health stuff and her husband did everything for her. She had very expensive taste and bought the finest of stuff, including a brand new Hummer. Her husband retired and it should have been a good time in their life, but I think he worked more because she always wanted something done. He looked more stressed after retirement. Oh he grumbled and said no to her, but then always gave in. The man was never sick a day in his life, and 2 yrs after retirement, he had a massive heart attack and died during his sleep.
Reading your post reminded me of my brother in law who always took care of everything. Im betting your family see's you as the strong one that they can rely on, and never consider the real effects this is having on you. They can become strong while you are still here to see it. If you need to , get your wife to go to therapy with you for couples counseling. I know there are no guarantee's on how this will turn out, but your committment at this point in life is to your wife, and her to you. Time to see the future in the next chapter of life.