It is complicated. If it is due to a flaw in one of the X or Y chromosomes, that greatly changes the calculation. Dominant/recessive categories changes the math.
But ignoring all that, it seems like you have the same risk as your parents: for them, there is a 50% chance they got it from one known carrier; for you, there is a 25% change of having gotten it from each of two known carriers.
Also ignoring gene to gene interactions that can have adative or worse effects.
In his case, it probably is associated with the fact that he worked with agrochemicals his whole life, in a time when regulations and PPE where much loosier. He tells stories of taking baths of substances while his dad worked in orchards.
https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC4832962/
"Organophosphate poisoning is highly lethal as organophosphates, which are commonly found in insecticides and nerve agents, cause irreversible phosphorylation and inactivation of acetylcholinesterase (AChE), leading to neuromuscular disorders via accumulation of acetylcholine in the body."
It affects people differently. For some it strikes the feet and legs first, for some the arms and neck. Some people like Stephen Hawking live with it for years, some only survive a year or two after diagnosis.
It's rare, so diagnosis is often preceeded by wrong guesses at more common explanations for the symptoms. There is no test for it; it's basically diagnosed by ruling out everything else.
I often worry about the genetic implications of this. If the disease has any genetic predisposition, then I would certainly be out of luck. My mother and father are both well, approaching 60, but they would only have half of the genetic concern I do.
We just don't know. The disease remains a serious mystery to us.
I hope that in my lifetime, we are able to understand more about the disease, what causes it, and hopefully find a cure.