“Fossil fuels” are found throughout our solar system (on Titan, Neptune, Mars etc plus comets) but only on Earth are the vast majority of the same substances believed to be of biotic origin.
Jupiter alone has 10 million times more methane than Earth does and all of Jupiter’s is presumably abiotic.
IMO the abiotic theory merits more study and perhaps alternative explanations for the biotic markers found in Earth’s fossil fuels can be found
Yes, it’s mainly all light stuff like methane or ethane. The liquids and bigger gas molecules (which we use) are the result of something else, probably an organic process.
Bigger molecules absolutely can be created out of the light gases chemically, but it’s quite the intentional process (that’s what happens in LNG plants) and unlikely to have occurred naturally, let alone all over the planet, while there are a ton of biological ways it happens.
So it’s much more likely to be biological.
Not saying you’re wrong, mind you. But probably not.