MIL with dementia

That sounds rough. Time for some hard conversations. Start with your husband: what is his view for his parents ' care over the long term? What is he doing now, and what would he be willing to add as their needs increase? What about when they need 24/7 on site supervision, need to be bathed, dressed, diapered, fed? What if you were not available or capable to help? If he is adamant that they stay in their own home, he needs to pick up more of the support tasks and/or provide for some in-home paid caregiving so that you are not crushed under the load.

I hope that you and your DH can come up with a united plan to then meet with the siblings and discuss a more equitable distribution of caregiving. In most families, there will be one child who ends up shouldering most of the day to day care. Can you give the sibs specifics on what you need them to do to allow you and DH some breathing room? Could you take a weekend (or longer) away and trust that one of the sibs would cover the care needed? Could the local sib take a whole week each month to do everything you do? What is the backup plan if you or DH becomes ill and cannot provide the level of care that you give now?

If the sibs can't or won't help to the extent that you need, they need to know that you and DH will decide when you are ready to make plans for the parents to go into facility care. Who has power of attorney for decisions like these? Sibs should be made aware that you expect their full support when the time comes that you cannot continue the present arrangement. It sounds as if you are there already in terms of caregiver stress.

Welcome to the group! You are doing a lot. On top of that you're being verbally abused by your MIL, adding to your stress even further, so the road to burnout is going to much shorter, if you're not already there. (The warning lights are flashing.)

This is as much a marriage issue as a caregiving issue.

What tasks is your husband doing? These are his parents, so he should be doing the lion's share along with his siblings. Does he see the two of you taking on an ever-increasing caregiving load for the next 10-15+ years? (Those longevity estimates for dementia are vastly underestimated in my experience.)

Does he know that caregivers for people with dementia have a 50% chance of dying BEFORE the person with dementia? I'm sure it's higher caring for 2 people with dementia.

What about your parents - do you have or will you have caregiving obligations to them? Maybe it's time for you to take some time away from home to check in on them or a long lost friend. That way your husband can get a better picture of all that you're doing and figure out alternative solutions that involve less hands on caregiving. Remember, as long as you are the solution, they won't bother looking for alternatives.