DPF's are an absolute nightmare if you use them in the wrong way.
Or should i say incompatible way.
One thing. Does your regenerate with an additive or is it the kind that injects extra fuel and alters the timing.
Admittedly going by your fuel contamination I suspect it is the non additive type.
One suggestion that i have used to good effect.
Try an recognise when the DPF is in active regen. May sound like a slight misfire. And the exhaust sounds almost boomy.
When it is convenient never switch off till regen has completed.
Another way to spot it is when ticking over with an instant fuel consumption readout you will see tickover instant consumption go from 0.1 or 0.2 g/hr up to 0.5 or 0.7 g/hr.
Also if you are able to fit a runlock system then you can leave the engine running without the key and the doors locked.
When using the Zafira response cars I would use runlock when I got to an emergency call so that I could leave it to regen on its own, obviously only if it started an active regen enroute.
I managed to go two years without causing a dpf related limp mode (dpf over 75%) but still had to content with regular eml lights caused by the egr!
My Volvo is a 2007 model registered in 2008. But was bought because it was Euro 4 with no dpf.
Wifes Clio is also the year before the dpf ( or FAP in Renault speak)
Pathfinder, well no issues so far. But putting a bit away as I want the dpf out soon as.
When dpf is gone I can either use the 10w40 Mobil Delvac oil I am going to use in the Taxi or use the same Mobil 1 New Life 0w40.
Though on price it has to be Delvac.
Almost £10 cheaper a gallon!