It does sound like something is wrong with your father, like he's had a drastic personality change. I'm assuming that he used to take care of things around the house and has suddenly stopped.

Could you have a conversation with your mother, one that she wouldn't repeat to your father? She may have some ideas about what's wrong with him. Could you contact his doctor or arrange for him to see someone? Is it possible that he has some sort of injury that prevents him from working, but he doesn't want to admit it to anyone?

What you and your siblings can do may be limited if your parents aren't interested in sorting out their own situation. They are who they are. You can't make your father get more work or make your mother more assertive, no matter how much better their lives would be

It's really a shame that your mother won't let you come over and help fix the place up.