Stranger abductions are rarer that parental murders. Approx 100 per year. The stats provided here aren't detail specific to Dylan's age/gender either. And stats don't exactly tell the story. The elements of the crime tell the story. And that varies crime to crime.
I assume you mean stereotypical kidnappings? 115 per year? They're not all strangers.
Anyway, the 125 to 150 murders per year are by fathers
and all other family members combined, so they're about equal. Fathers may be a bit less.
I agree that the numbers don't tell the whole story, and that the elements of the crime can give us some clues. Here, we have no elements.
You have to make up so much stuff to get to a murder-by-Mark theory. You have to make up that Mark was drinking, make up that Mark and Dylan had a fight, you have to make up a reason for the fight, make up that Mark took Dylan's phone, make up that Mark broke Dylan's phone, you have to make up that Mark was killing Dylan to get back at Elaine, and on and on and on.
(I don't mean you specifically by the way - it's a general you.)
Add to that that LE have said that Mark is not considered a suspect and you have to make up that Mark is "the unnamed suspect" or "the unnamed POI".
Add to that that LE haven't mentioned any evidence of what would statistically be a very violent crime, so you have to make up blood or brain tissue or decomp fluid.
Add to that that nobody's mentioned any signs of a fight at all, and you have to make neighbors hearing screams or yelling or cursing, scuff marks on the walls, a broken vase.
Add to that that Dylan's mom and other family members have stated that they don't think Mark killed Dylan.
Phew! I could go on, but there's the gist of it. There's just too darn much I'd have to make up, too many explanations I'd have to come up with, to go with the murder-by-Mark theory.