Buy a ceiling hugger style fan (the ones without a stem or with the option to mount without the stem).
Mount the fan's bracket directly to the ceiling with toggle bolts or other such fastener. This way the fan is not support by the box at all.
Good luck with your project!
What you have there is a perfectly standard, and to modern code, switch loop. And every wire is where it belongs.
It seems that the fixture is using the red (as the live?) from 1 cable...
If the above is correct, why was this necessary? What is the red wire's purpose - where does it originate from? Were the 2 blacks also live?
You're puzzled at why if the red is live, why are the blacks there too? Let me ask you this: how does the light know when to be on, and when to be off? Do you want this light to be on at all times?
That's right. You need a "hot" wire that is on, only when you want the light on. That is called the switched-hot and that just gave it away. Ideally, it's nice if switched-hot is red.
Now where do you suppose the switch gets hotness from? It's not magic. It gets it from another wire, that is always-hot. The switch either connects always-hot to switched-hot, or it does not. Always-hot is usually black.
What about neutral? Neutral returns the current to source. (sorta like hydraulics, you plumb a return pipe, or you'll get a huge oily mess all over your shop floor.) The lamp needs neutral, it goes between switched-hot and neutral just as you see. Code requires neutral be white (or gray, but you'll never see that).
Now you are thinking. Wait. Why does a switch need neutral? That switch doesn't. But if you ever change it to a smart switch, it will, and accommodating those is a 2011 Code requirement. Switch loops must be /3 cable:
- neutral must be white
- always-hot is conventionally black
- switched-hot is red because it's possible here.
And as it works out, this box is perfectly color coded, the colors always match the functions. That is often not possible (though it's always fair game to color-code wires with tape).
The lamp doesn't need always-hot, so it just passes on through. The left /2 cable brings power in, the right /3 cable to the switch is a spur.
Best Answer
Your dimmer is not compatible with your wiring
Your house appears to be wired in late-stage knob-and-tube, with only the hot wires (incoming and outgoing) present in the box and the neutral bypassing it. As a result, you do not have a neutral in the box, which is what your dimmers require to power all the "smart" electronics inside them. You'll either need to use a "smart" dimmer that trickles power through the load, such as the no-neutral version of the Lutron Caseta (and perhaps LUT-MLCs in the fixtures to keep your lightbulbs from glowing or flickering due to that trickle of power), or have the neutral rerouted into the box, which'll require an electrician who's familiar with knob-and-tube stuff.