How do I get my verbally abusive hoarding father to stop hurting my mother w/o losing their home or jailtime?

I moved back in with my parents last summer because I couldn't find a full-time job after graduating last June and can't even pay my own bills. Now that I'm living here, I can't avoid noticing how my father's hoarding has worsened and how it's affecting my mother. Neither of us dares to even bring up the subject because it ALWAYS results in him yelling and screaming at us. I also risk losing a place to sleep if I upset him. However, this is how we are forced to live:

The only cleared counter spaces in the entire kitchen are in front of the microwave door and inside the fridge on the ledge below the fridge door. I actually have to turn sideways in order to walk through the kitchen and living room. In the living room, there are two chairs that remain clean so my parents can sit there. There's a couch behind the chairs that hasn't been used in years but it's piled high with things and my father screams at me any time I mention giving it away or getting rid of it. Items are literally stacked to the ceiling in many places. I have to sit in the computer room because there's no cleared spot in the living room for me. I eat on the space where the mouse goes because it's the only space not stacked literally to the ceiling with boxes etc.

Out of the four bedrooms in the house, he's filled 2 and my sister has filled the other 2 (including what used to be my bedroom...my clothes and toiletry items are in two laundry baskets on the bed because it's the only available space). My sister is also a hoarder who's emotionally unstable so I dare not risk her life in order to get her to throw anything out...she's been in counseling for years and still can't throw anything out)

My father also cooks expired food. We're not talking about last night's meatloaf here either. I have been eating fast food and frozen meals (the 3 chest freezers are full so I can only buy one a day and eat it right away) for the past five months. The only time I ate what he cooked...I found small beatles in it after a few bites. When I checked the package, I discovered the instant potatoes were two years expired..and he knew before he cooked them. His response...he laughed at me and said, "it's only a bug, what's the big deal?". He won't even let me throw out moldy cheese! Oh, btw...we have fruit flies all the time...and most recently...rats. Yes, rats. I've even watched one drink out of the kitchen sink. I don't dare call the exterminator because they'd call the city and we'd be kicked out because it's a safety/fire hazard.

My mother has to have surgery which is why I'm asking for advice. After her surgery she has to live on the main level of their house for 3 months (only bathroom in the house is on this floor) but there's no place for a bed. My father refuses to move anything because the house is so full of stuff there's no place to put it. He won't throw anything away or even put anything in storage. We can't afford to get our own place because my mother has to pay the thousands of dollars in credit cards every month that he spent behind her back...and she won't divorce him because she fears being alone. He won't go to counseling either, I already tried and he nearly hit me for asking. She can barely walk, but without a place to lie flat (doctor's orders), she can't book the surgery.

My question is this - How can I fix this situation without making my mother's situation even worse?