At what fuel state can you bend the rules?
At a suitable time prior to bending the aeroplane.
When you find yourself in a **** situation, you need to realise that eventually, one way or another you will end up descending below the MDA, like it or not.
Now answer this question, do you prefer doing it with enough fuel to do a MA and come back a second time? Most of us yes. Because nobody wants to do it with two flame outs at 5 miles out.
Better to be bending rules in a planned controlled and safe manner than breaking them in a complete state of misery.
I was dumped on a few years back for suggesting a two plot crew should have developed a plan using all their resources and executing a below minima landing on a long bitumen runway while runway aligned. Some did not get it then, and it seems some don't still. I beats an uncontrolled ditching in the ocean or countryside by a long margin.
Best not to find yourself there in the first place, but they did. No point making a catastrophe out of a **** situation.