You are wise to write. Some difficulties have to be taken beyond the family into community services working together. Your job as caregiver to your parents will be to help
coordinate and communicate.
I would suggest two approaches to start. To get a fire inspection go to the nearest fire station and find out the process in your county to get you father's house inspected by the fire marshall.
This will enter your father and your family into a process of seeing whether he will be able to clear up the mess or to have the house condemned. Since your dear father has refused to listen to the family, you have no other choice.
I would also suggest that you contact social services for your county.
Sometimes we fail to get treatment for our parents, after they are old, because it is hard to deal with the anger. Also, it sometimes takes more official channels. Your father needs help. He may not be competent at this point to deal with his life. Your mother, probably out of old habit, wants the familiarity of her home whether it is safe or not.
After consultations with these two county agencies, if you need further assistance, please write back. You have extended yourself. You have taken care of your mother. Now you are going to get some help.
You may need a support group. You are moving. You are expanding. You have been solitary family helpers. Now you will become part of the team of people needed to sort this out.
Don't give up, people have to work together.