It's possible, I am no expert you understand, that the fuel system is 'toast' , kaput, no good.
If I understand you right , you have a Derv ,you a cidently fuelled with Petrol, you would've be the first to have done it, I confess I have.
I too accidently put petrol in a Derv. In my older mk 2, I realized very quickly that I had , immediately switched to Diesel filled to the brim.
The problem here is the derv fuel system works on a very high pressure system, petrol will ruin it, as soon as you attempt to start the car, even before the engine is turned over, the high pressure system is running.
So driving a short distance with petrol, is going to wreck the fuel system.
I got lucky I realized my mistake, they say if you mis fuel, don't even attempt to run the engine, have the system drained ,cleaned, and refilled, myself I drove less than 1 km to a friend's house, and asked what to to do, fortunately the old 1.9 PD is a tough old engine, ,....because only put a few litres of petrol I. ,I diluted it with another 55 of Derv, friend said it might run rough, but keep filling it up, it might be ok.
That's what happened in the end , it was containimated but it ran fine ,untill I sold it on at 100, ooo miles on the clock.
So , I believe that's the case with you, the injectors and high pressure system derv pump is no good, had you dropped and cleaned the tank, you might have be Ok , your 5 km just might have been to much on a tankfull of petrol.