@buggirl55 Oh, I know you have your hands full. I found this helpful blog post (not scholarly, but very helpful) that may give you some good ideas.
https://makedementiayourbitch.com/dementia-poop-how-to-avoid-accidents-and-stop-smearing/
It is common for those with dementia to start soiling themselves and everything around them. Maybe your dad could give you an estimate of what time this usually happens and you can figure some strategies from there
You might also ask around about family medical leave.
https://www.dol.gov/agencies/whd/fmla/general-guidance
This would give you the needed time to observe what is happening and to discuss, with others, some solutions.
Is this a possibility for you?