Just need to vent here; any advice?

I'm both POA and trustee for my dad but his sister has health power of attorney which, I think, just covers end of life? Anyway being POA and trustee is problematic now because dad is in another state with my brother and sister in law and he will say he hates it but he also says he doesn't want to come to my state (Nevada). It's become problematic because he can't hear a thing and I have to communicate questions etc over the phone. It's also problematic because my brother and sister both work and whenever I need something done, they make a promise but they take months...even 6 months to do it. If I put too much pressure on them, then I get blistering abusive phone calls and emails and I'm just sick of it. I don't want to be trustee anymore but my brother, who's listed next in line is totally irresponsible with money... and we're talking money like he's never even dreamed dad has. I'm better suited to it because I'm a CPA and dad trusts me but this abusive behavior and neglect of stuff I need (like a letter from a doctor, a copy of keys, an item for his tax return)... just gets ignored. They admit they screen my phone calls and don't read my emails. It's not working and it has ruined any hope of a relationship between us... I think it's torture for them too. I am not sure what to look for to find a third party to help or even if I can do that? I have begged dad to move here so I can talk to him face to face and get him to understand. We would try it here at home but ultimately I think I would put him in assisted living or memory care if he gets worse. (He also has dementia but he knows I would do that and I think that's part of the problem.). Can I simply go get him since I'm trustee? If not, can I find someone else to be co-trustee in the other state even though my brother is supposed to succeed me... someone that will make them tow the line? My brother makes a pittance for his care and board for dad but it is the amount dad said to pay. I get nothing for doing all the rest and putting up with my brother's screaming. It's just a mess and getting worse the less dad understands and hears. Ok, rant over.