The problem with this theory is that it wasn't the dinosaurs only that whent extinct. Plants, fish, sea-reptiles, amphibians etc.. also where affected. Amphibians would actually benefit from insect increase, because for most amphibians, insects are the main food source.

Not if the insects were poisonous or diseased. I'm not sure this quite warrants the use of the word "theory" yet either.

But, and I only throw this in as another thing to consider, not a definitive answer, if you remove one substantial section of an ecosystem, it will have a profound, and often unpredictable effects on other parts of that ecosystem.

So if you remove a substantial proportion of the herbivores, you may well decrease the amount of nitrates going into the water table, which in turn would affect algal growth, which would then in turn result in a food shortage for the the larval stage of most amphibians.

And of course, the ones that do make it to adulthood would be vulnerable to the insect carried diseases.

The amphibians would be a food source for carnivorous fish, etc. and so the ripples spread across the pond.

But yeah, I think if this was involved, then at best it was a factor, not the complete cause.

Just like Jurassic Park said!