I’m so sorry you’re facing such an awful situation.
Of course YANBU. Your focus should absolutely be on your son and everyone’s else’s wants/needs are frankly irrelevant.
Anyone whose not supportive/helpful does not have to be tolerated.
I’m not sure if you’ve heard of the Ring Theory of support. I’ve copied it below. Frankly I don’t think showing it to your PIL’s would help but it might be worth speaking to your DH about - a good tool to explain exactly why his parents need to back off. Essentially they are refusing to accept their proper place in the ring - outside your son and you/your DH. They are putting themselves in the centre and making your son’s illness and treatment “about them” when it’s not - they are 3 times removed from this and need to act appropriately. If they can’t do that, then they simply have no place in the ring at all.
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Ring Theory of Support
When there's a critical sickness or death in your social circle, emotions necessarily run high. Using the Ring Theory can help determine who to comfort and who to vent to.
While it's often obvious at the outset who needs the most attention (the person who is sick) but as time wears on, needs can get mixed up:
When Susan had breast cancer, we heard a lot of lame remarks, but our favorite came from one of Susan's colleagues. She wanted, she needed, to visit Susan after the surgery, but Susan didn't feel like having visitors, and she said so. Her colleague's response? "This isn't just about you."
"It's not?" Susan wondered. "My breast cancer is not about me? It's about you?"
The same theme came up again when our friend Katie had a brain aneurysm. She was in intensive care for a long time and finally got out and into a step-down unit. She was no longer covered with tubes and lines and monitors, but she was still in rough shape. A friend came and saw her and then stepped into the hall with Katie's husband, Pat. "I wasn't prepared for this," she told him. "I don't know if I can handle it."
This woman loves Katie, and she said what she did because the sight of Katie in this condition moved her so deeply. But it was the wrong thing to say. And it was wrong in the same way Susan's colleague's remark was wrong.
To avoid being unintentionally insensitive, Susan developed Ring Theory, which works like this...
Draw a circle. This is the center ring. In it, put the name of the person at the center of the current trauma. For Katie's aneurysm, that's Katie. Now draw a larger circle around the first one. In that ring put the name of the person next closest to the trauma. In the case of Katie's aneurysm, that was Katie's husband, Pat. Repeat the process as many times as you need to. In each larger ring put the next closest people. Parents and children before more distant relatives. Intimate friends in smaller rings, less intimate friends in larger ones. When you are done you have a Kvetching Order. One of Susan's patients found it useful to tape it to her refrigerator.
Here are the rules. The person in the center ring can say anything she wants to anyone, anywhere. She can kvetch and complain and whine and moan and curse the heavens and say, "Life is unfair" and "Why me?" That's the one payoff for being in the center ring.
Everyone else can say those things too, but only to people in larger rings.
When you are talking to a person in a ring smaller than yours, someone closer to the center of the crisis, the goal is to help. Listening is often more helpful than talking. But if you're going to open your mouth, ask yourself if what you are about to say is likely to provide comfort and support. If it isn't, don't say it.
Don't, for example, give advice. People who are suffering from trauma don't need advice. They need comfort and support. So say, "I'm sorry" or "This must really be hard for you" or "Can I bring you a pot roast?" Don't say, "You should hear what happened to me" or "Here's what I would do if I were you." And don't say, "This is really bringing me down."
If you want to scream or cry or complain, if you want to tell someone how shocked you are or how icky you feel, or whine about how it reminds you of all the terrible things that have happened to you lately, that's fine. It's a perfectly normal response. Just do it to someone in a bigger ring.
Comfort IN, dump OUT.
There was nothing wrong with Katie's friend saying she was not prepared for how horrible Katie looked, or even that she didn't think she could handle it. The mistake was that she said those things to Pat. She dumped IN.
Complaining to someone in a smaller ring than yours doesn't do either of you any good. On the other hand, being supportive to her principal caregiver may be the best thing you can do for the patient.
Most of us know this. Almost nobody would complain to the patient about how rotten she looks. Almost no one would say that looking at her makes them think of the fragility of life and their own closeness to death. In other words, we know enough not to dump into the center ring. Ring Theory merely expands that intuition and makes it more concrete: Don't just avoid dumping into the center ring, avoid dumping into any ring smaller than your own.