What To Do with my father in law?

My Father In-Law has been with us for over 2 yrs his older son send him to us because he was remarrying and he did not have room. my father in-law never had medical attention when he was with his older son in another state. When he first arrive with us we seeked medical help for him we noticed he would talk to himself and he would sleep alot he would'nt want to do anything but get up go to the restroom and eat drink cokes and sandwiches all day. So the Dr. started him on meds. and diagnozed him with severe depression & schiznoprenia. Well he is doing better now on meds though. He started going to an adult day care and this is the second time we have moved him to a different center because of the same issue. He gets infatuated with this women and we come to find out that this women are only intersted in him because he recieves a monthly pension as a veteran. He has been talking to this particular lady and she is a gold digger she just takes advantage of him. My husband gives him money from his pension so we notice he would ask for more frequently and well we got to the bottom of it now we are more careful with that. But, now my father in law talks nonsense he wants to get married and move in with this lady I don't get it. I spoke to the lady she said she only wanted to be friends with him but it seems that she keeps leading him on or my father in-law is obssessed and can't realize the reality of a friendship and a serious relationship. He has been divorced for 20 yrs. When this issue happend with the other lady at a different center he went into a big depression and almos hit rock bottom again though we helped him out alot. He says we control his life and that we don't give him liberty mind you he is a 60 yr old recovering alcaholic who is schizoprenic,has obsessive control dissorder, severe depression, mild dementia is and aggressive at times. How can we solve this issue the Dr. does not want him living on his own he said it is best to live with his relatives and we are his only option no one else can care for him and he does not want to go to a nursing home. I am so stressed out I don't know what else to do? It is like taking care of another child. We are afraid that if he does move in with this women or any other women who don't care he will end up homeless again like he use to be before he moved in with his older son and that he will destroy his life completly. We have spoken to the Dr. about this issue and he really does not give him much advice. They said we cannot get power of attorney over him anymore because he is mentally disabled already the doent wont be valid and inorder for us to get a court order from a judge he needs to be a threat to others and himself and at this point he has not gotten to that point and we are greatful but how can we take care of someone that wont allow us to? What do we Do?