You seem to have two separate questions between the one in your title and in your description. No other figure in automotive history has been written about more than Henry Ford, or in even in American history for that matter. And, in all that writing one of the biggest issues is his character.

If you can find a copy of it, I would suggest reading Robert Lacey's Ford, the Men and the Machine. I still think it's the best book written on him that deals with his whole life in relation to his family, friends, era, and location; all of which are important to understand to be able to answer your first question. Also, Steven Watts' The People's Tycoon is another well written biography. It focuses more on Ford himself, but tries to dig deeper into his psyche.

To answer your second question, Ford didn't invent the automobile. He was one of many experimenting with it at the time. His first efforts were far from unique. He wasn't the first to come up with the idea of a mass-produced car, or even the assembly line. The idea of selling a cheaper, more reliable, or versatile car wasn't his either.

Instead, it was Ford's relentless pursuit of cost cutting and greater efficiency that kept driving the price down, coupled with unique marketing and promotion that drove demand up. Others would surely have come along and done the same thing. However, Ford's advantage was his timing. He did them first, and he generally stayed ahead of his competitors just enough to give Ford 50% of the market for almost a couple of decades. When the competition did catch up though, it was nearly a disaster for Ford.

So, in my opinion, the answer is the industry would have grown marginally slower, but I think it would have eventually been just as big.