How can I get my brother, who is the Executor, to contribute more time to help watch my Mom so I can get some respite time?

Speak plainly to him. Stop asking him to help with HIS mother who he is Executor and I'm assuming POA for and has access to her money.
You are not his employee so you do not have to "request" time off from him.
Write down what hours or days you want or need off. Then give it to him and tell him to make an alternative care arrangement. Of course offer to help with finding the alternative care needed even though he's one "in charge" so it's his job and responsibility to do this. If you have a special occasion planned and need a different day off, or a few for something give it to him in writing (plain English) and a week or two notice to find respite for mom.
If he fails to do his duty, if no caregiver shows up for respite care, put your mother in the car and drive her over to his house and drop her off.
Remember something. Your brother is the one getting off easy here because he doesn't have to do any of the actual day to day care himself for your mother. This does not mean that he can shirk what are his responsibilities. Stop allowing him to neglect his duty before it turns to real resentment for you.

Say instead you need $$$ for a live in caregiver so you can go on vacation. He has to be advocate & stop by each day you’re away. . I would test out caregiver before you go…by having her stay a few hours a day for at least a couple weeks. Make sure you lock your valuables..or another idea is to put her in facility for a couple weeks..& brother can visit. Hugs 🤗

Is he also POA? Tell him the care of Mom is getting too much. That if he refuses to help in her care then you want a caregiver hired. If he is not for that then tell him he will need to place Mom because you can no longer do the care.

Some POAs try to save money so there is more to inherit. But, Moms money is there for her care.

It would help to know if your mom had assigned one of you as PoA? If not, and since you are the primary caregiver, who is managing her financial affairs? If your mom has no PoA and her dementia is beyond what an attorney would find as capable of understanding creating or changing one, then whoever is currently managing her money needs to be very very careful and informed about how to do it. Your mom may eventually need facility care which may require Medicaid to pay for it. Medicaid rules differ by state, and the application has a "look-back" period of anywhere between 2.5 and 5 years. Many well-meaning people have caused their LO to be delayed or disqualified because they didn't know the rules in advance. I strongly recommend you use her funds to consult with an elder law attorney regarding PoA, and a Medicaid planner so that you know where she stands should she ever need it.

Does your mom have an actual medical diagnosis of dementia by her doctor? How advanced is it? If it's mostly memory impairment she may still be able to create or change a PoA. An attorney would interview her privately to see what she can comprehend. Memory is not that much of an issue in this, understanding is.

It is true that your brother is under no obligation to help care for her. Neither of you should be paying for her living expenses or care, as this is unsustainable. Have you considered adult day care? Or contacting social services for your county to have an in-home needs assessment for her? If she qualifies she can receive some light housekeeping, meal prep, help with hygiene, etc. Please provide more information about your situation if you can.

Use moms money to pay for an aid to come in on a regular basis.

Your brother has made it clear that he won't be doing any care, he is not obligated to. So, you pay someone to help her.

Hopefully you are getting paid to house and feed her, at a minimum. Your efforts should not secure his inheritance.

Executor does not come into effect until after death, so it is a mute point, unless he is using that to control moms money. If that is the case, it is time to get an attorney for mom so that she can pay for her care.

You sound like you are getting overloaded. I can understand that & also how resentment can build.

You have asked your Brother, he has said no. So. What's next?

You could ask nicely, plead, push, lay on the guilt... He can still say no plus your relationship will suffer.

What if he lived 3 states away, had an illness himself or you didn't have a sibling at all - what would you do instead? Who else could you ask? Have you looked into aging services or home help in your area at all?

When caring for others, it's a great start to look after yourself too. Put your own oxygen on first etc. If your Brother can't hand you the oxygen, find others that can.

You Can't

Sorry

Please know that being the executor does not give your brother authority while your mom is still living. A judge has to approve him even then.

Look for your area agency on aging. Call them and ask for an assessment of your and moms needs. See what services are available. Depending on moms insurance, home health care is available as a benefit for homebound seniors who have health issues. She may even qualify for hospice which can include respite. Check out the various services offered by organizations that better understand what you are going through. Don’t discount small layers of help. It can make a difference.
See if your own insurance has provisions for therapy.
It’s very disappointing to be mistreated by family. I get that. Refocus on looking where there is help available. Resenting your brother puts an additional emotional burden on you.

Sheri, you can’t force your brother to do better. Being the executor is stated in the will, and only kicks in to administer the estate after your mother has died. Does he have a Power of Attorney now? Is there one?

A line you could use is to say that you are reaching the end of your ability to cope, and if you can’t get some relief your mother may need to go into a facility for care. This will be very expensive and will eat up most of her capital. If he can’t manage to give you a break himself, could he pay and arrange for a carer? You can’t afford it, and it would be cheaper than running down her estate with a facility. If he pleads poverty, then mother’s money should pay, and you give the impression that he would need to OK that..

Even if you don’t really mean this, eventually it may be true. It is quite possible that your brother will either rethink his unwillingness to help, or follow the suggestion of arranging a carer to help. With highly resistant family members, money is often a strong motivation. If he doesn’t know the normal cost of what you are providing, it’s time he found out. Good luck!