I guess legally you may be out of luck here - unless you still have some of the gas left and you are willing to pay several thousand Dollars for an in-depth Analysis at an Independent laboratory, with an unknown result.
However I do have a suspicion how all this talk of diesel/non-diesel and "bad fuel" might have come about. Some backstory:
I am regularly ordering large deliveries of marine fuel in your area.
Since we are speaking of several thousand metric tonnes per delivery,
there are representative samples taken, which are then analyzed in an independent laboratory like SGS, Inspectorate, ect.
Think of it like a Blackstone labs oil analysis, just with more parameters.
So, what is happening since a few months is that we are experiencing random problems during burning of These fuels, even though the regular analyses are completely okay.
So far, this happened with fuels taken in the area around Florida, as well as New York and Balboa.
Enter the gas-chromatographic/mass-spectrometic analysis on vacuum distillation (basically ripping the fuel apart into ist very contents on a molecular level, and quantifying the contents, for some 15.000 dollars a shot):
Turns out that most of the oil majors started increasing the FAME (Fatty Acid Methyl Esters) content in all of their fuels (marine fuels, consumer gasoline, industrial blends, ...), right in the refineries.
In one case, the German air force even had to detain their jets because this stuff was
found to be present in the jet fuel (delivered via a NATO pipeline...).
FAME is basically a mixture of fat and alcohol, typically found in bio-derived fuels, like bio-diesel.
It is cheaper to produce than oil-based products and does not originate from the regular cracking-processes in refineries.
Legally, they are allowed to do this (as long as they sell their stuff as per ISO specifications like ISO8217), but the more of this stuff is mixed in, the more likely we have found catastrophic engine failure to be.
Does not matter if we are talking about 2-stroke or 4-stroke engines, diesel or gasoline.
If there is enough FAME-content in a fuel batch, some automated testing methods may even mistake this blend as diesel instead of petrol/gasoline.
What we have seen so far is laquering of the fuel System components (high pressure fuel pumps, fuel lines, filters) as well as loss of cylinder lubrication due to the high alcohol content, and extensive wear on all effected components until the point of catastrophie failure.
Sorry for the wall of text, this just came to my mind, as I have had this interesting discussion last week with the Chief chemist at SGS.
Maybe you can have a look at the internals of the replaced fuel pump?
If it does look clogged up, or it was painted with shiny enamel, you might have something to support this theory.