Husband and I are primary caregivers to declining MIL. I provide direct care. Hospice is 1x a week. BIL in distant state is full POA. Any advise on future care decisions?

Our County government offers caregiving workers 3 times a week for two hours a day at no cost. The workers are monitored and are provided ongoing training and supervision year round. Their workers abide by County rules for caregiving. The department is called senior or elderly services. Had a few things I had to address with one workers supervisors but after that no problems. Medicare will also pay caregivers like family for instance. Inquire with the health plan. A background check is required. Agencies are expensive and private hires have no one to report to.

If you are not her PoA and she is now "incapacited" so that the PoA authority is now active, then you have no ability to make medical or financial or housing decisions for her.

If she still has enough "capacity" and (which an attorney will determine through a private interview with her) and does not have a medical diagnosis of cognitive impairment in her records, then she still may be able to change her PoA (if you want it to be you). Capacity has more to do with comprehension than retention, so even if she has poor short-term memory but has mild cognitive decline, the attorney may judge she can reassign her PoA.

Otherwise your only other real options are what AlvaDeer laid out.

What do you mean Hospice 1x a week. A nurse should be there at least 2x a week, as should an aide. I may change Hospice providers if this is all the help u get.

This is why those caring for someone should also be the POA. Your BIL is trying to save his inheritance while you do all the work, as said, time for an elder lawyer who can demand that POA contact him with financial information. Also informing POA that he has responsibility to his mother. He should at least be sending you her SS each month. You should not be spending any of ur own money on her if she has her own. A complaint to SS that he is not giving her her SS could be done.

You need to see an elder law attorney. You need temporary guardianship. Should MIL go to hospital this may be easily done. You have a POA who will not communicate with the caregiver. That's a no-go for certain. If she goes to hospital ask to speak to a Social Worker and try for emergency temporary guardianship. The bills will go to BIL as POA for payment if he has control over the account.
The elder law attorney will give you your options.
If all else fails you are down to an attempt at ER dump which means you refer the hospital to the POA and you refuse to take MIL back saying you are physically and mentally unable to care for her and he will not speak to you. This will however be complicated at this point as you have made YOUR HOME her home now. She lives there and is considered at HOME there, a tenant whether she pays rent or not.
See an attorney today. Have billings sent to the POA if he handles the finances.