Months ago, when the whole jab thing started, my mother and father in law were determined to get it, because TV told them so.
I advised them not to, and that they are going to damage themselves, multiple times, I event told them about how I ended paralised for a month as a kid when I received vaccine back then... Nothing... They went and did it. 3 times. So after that I basically told them I don't want to talk about it anymore.
Now my father in law, months later, as expected, got a serious pneumonia, lost ability to walk, or even sit in bed, lost control of his bowel movements, and ability to talk, so we are taking care of him the best we could trying not to loose our minds in the process... Showing up with a smile, trying to make their life easier, paying for bills, paying for medication, paying for diapers, and food, clipping his toe nails, cutting his hair and beard, changing diapers...
So on top of all that, wife and I were "politely asked" last night to respect my brother in law more, since he feels that "a lot is depending on him". Same brother in law who was organising excursions with the rest of the family to go for a group testing, to see what might be wrong with them... The same guy who cannot lift a bed matrace without having 2 people help him, while wife and I are the ones carrying his immobilised father around... Same guys who can buy both wife and me with his salary but is paying way less for their bad decisions, and the first thing he came to us with was "how are we going to divide the expanses"...
So I snapped, and yelled my lungs off. So my brother in laws, hypochondriac ass was insisting on them getting jabbed. They did it and we are stoically dealing with the damage made, because they are our parents. And I am accused that I am not "respecting" him enough by not being knowledgeable in ins and outs of hospitals and doctors and procedures and not getting the ideas "first" about where to drag the patient, next...
I am not proud of myself, my friends. I did not have "I told you so" moment at any point there. But I think that even the neighbors in next building heard about the boundaries that they will never be allowed to fucking cross with me...
The messed up thing is that I feel like a piece of shit, now, for allowing myself to go full dark mode.
Figure out what kind of "guilt" you are experiencing.
There is the guilt when we've done something wrong and we know it. This can be rectified by apologizing for our bad or inappropriate behavior.
Then there is anger that is converted into "guilt" because expressing anger was not acceptable in our families. This is the one I had to learn to deal with, and also sounds like what you may be experiencing. I never felt the anger building inside, but always felt "guilty". Once I learned this, I had to figure out how to handle it. So I would sit in my car (where no one could hear me) and go through all the things that "might" be making me mad. I would finally find it, and all hell would break loose inside that car, screaming, crying hysterically, calling all those people infringing on me all kinds of names, and the meltdown would last until all the words had been said, and there was nothing left to say. At that point, I was able to think rationally, and figure out how to handle the situation so that I didn't allow myself to get dumped on any more in that situation. Had to do this for multiple situations while learning how to take care of myself and my needs.
As bad as your father in law is, see if hospice can help. They can provide lists of caregivers so you can have a rest, a good hospital bed, diapers, baths, direction, spiritual guideance, etc. They understand what it's like to do care giving on a daily basis and can help talk you through issues and help bring some calmness to your life. Both my parents were on hospice, and the workers were sent by God. I was the only caregiver, and my closest family members conveniently "moved away", but tried to control my decisions. It was a mess, but hospice had my back, and I was able to hire some really caring people to help out.