Thing with Hezekiah is that though he's a 'good king', it's Josiah who goes full Yahweh on the worship of other gods. There's room to drive a pantheon of gods through the holes left around Hezekiah clearing out the temple.
The problem with the Egyptian link is that Palestine was, on and off, Egypt's playground. That there was a significant cultural presence is already known. But it doesn't seem to have played a direct role in the development of Yahweh. There's no evidence to support the Egypt > Yahweh idea. The scripture from 2 Chron. isn't really persuasive to me at all. Hezekiah may not even have been a Yahweh worshipper, and the seal itself doesn't make the link. The origins of Yahweh, to my mind, seem to follow the route all the way back to the Canaanite pantheon. (Frank Moore Cross' work still stands up.) I think there's ample evidence for Egyptian gods being worshipped in Canaan, Solomon's wife is the biblical reflection of it I guess. Maybe there were periods when they were the main culty thing to do.