I will answer chronologically. It depends on your definition of high in fructose, its right around 50%. And essentially the same as sucrose. I was trying to correct the misconception that there is much more fructose in HFCS then in table sugar. There isn't, it's pretty much the same. I was using this sort of discussion to lead into, well we know it's terrible for you and so is regular sucrose, and that is because of the fructose component.

Yep I know the story of where HFCS came from.

Oh lord. Starches are long chain sugars! Gucose syrup is indeed viscous because of long chain sugars for the same reason as HFCS, in glucose syrup the monomeric glucose component carries from around 10 to 90% depending on the grade of the syrup (coincidentally the viscosity would vary too), traces of other monomeric sugars like maltose are present. The remaining components there are long sugar chains of linked together glucose from the hydrolysis of starch.

The chain length is what gives both glucose syrup and HFCS their viscosity. Glucose by itself even at extremely high concentrations is still fairly non viscous, especially when compared to either of these solutions.

Thanks for reading and your comment!!