So why frogs? God could have pushed any other species to the point of infestation. Bed bugs, spiders, salamanders, crows, etc. So why frogs?

True, a frog infestation would be noisy, slimy, and perhaps even dangerous (poisonous). There was an easy fix, though, simply move away from water.

What were frogs to those living in the land of Misr (wrongly called Egypt)? Heket? What of it?

See Massey, Gerald: Egypt, the Light of the world over at Archive.org, volume-I:

The Frog which transformed from the tadpole condition was another Ideograph of female pubescence. This may be illustrated by a story that was told some time since by Miss Werner in the Contemporary Review which contains a specimen of primitive thought and its mode of expression in perfect survival. It happened that a native girl at Blantyre Mission was called by her mistress, a missionary's wife, to come and take charge of the baby. Her reply was, "Nchafuleni is not there; she is turned into a frog." (Werner, Contemporary Review, Sept., p. 378.) She could not come for a reason of Tapu, but said so typically in the language of animals. She had made that transformation which first occurs when the young girl changes into a woman. She might have said she was a serpent or a lizard or that she was in flower. But the frog that changed from a tadpole was also a type of her transformation, and she had figuratively become a frog for a few days of seclusion.

So you see, every creature as a symbolism of something human. Then later being appropriated with a different context, taking on a life of its own, leaving the lefty world full of salt at their loss.

Kekistan rules!