Trying to help ex husband with well organized delusions, any advice?

My ex husband is 85 and we have been divorced for years. He has no one else in this area to help him. He has always had a suspicious nature but it has gradually been getting worse. He is hard of hearing and about six months ago began having tinnitus but he said it was the neighbor pounding on his wall. I finally got him to an ENT doctor who removed some ear wax and recommended a hearing aid which he finally agreed to get but hasn’t done it. The delusions gradually increased until he has an elaborate scenario as to who is doing this and they are using radiation and special gas etc to target him. He stayed with me for a few weeks but since we only live a short distance apart they could get him there too. Now it has gotten to the point that he doesn’t stay in his house except for a short time. He drives around and sleeps in his car in random parking lots not too near his house so they can’t get to him. He’s having chest pain and headaches and dizziness but he refuses to go to his cardiologist because he can’t help unless he tells him the whole story and then they’ll think he’s crazy! He has 3 stents in his heart and is on plavix aspirin and two blood pressure meds all of which he has been on for a long time. Now he wants me to find him a body/security guard to patrol around him 24/7! We have two daughters one of whom lives on the other coast and the one who lives about 40 miles away has her own family. Neither one are close to him as he was not the greatest father. I don’t know what to do anymore. I usually just listen and encourage him to see the doctor but I am about at the point of telling him that all this stuff he says is impossible and letting him get furious. I’m no longer physically afraid of him but I don’t know what will happen if he feels I’ve abandoned him.