Everything you've said is discussed at length in the book.
I didn't say that being held hostage by your customers is the only reason that the Innovator's Dilemma is so hard to beat. There are a number of aspects to the theory and being held hostage is only one. I pointed it out only because we were talking about why people that are well aware of the Innovator's Dilemma (such as Clayton Christensen himself) mistake Tesla for a business with a sustaining technology rather than a disrupter. Many people miss the subtlety that traditional automakers (in the U.S. at least) sell to dealers, not to drivers. It is so telling that in order for Tesla to find success they had to find a new customer for their product. Elon has said, this would never work if they had to sell to the dealers. That is classic Innovator's Dilemma.
The traditional manufacturers are absolutely being held hostage by their customers as it is described in the book. That doesn't mean it is their only challenge. You pointed out some others. There are even more layed out in the book.
As for Tesla's future, I agree that it will eventually be on the wrong side of the Innovator's Dilemma. I just hope that they have the vision to see it happening, and that, either Elon is still there and has the ability to strong arm his company through the change (like a Steve Jobs). Or, if he is not there, that management has the presence of mind to take the easy road and spin of an entirely separate entity which is sized appropriately for the new market and made up of the best and brightest from the company with the intention that one day this new entity will overcome Tesla and that Tesla's shareholders will profit handsomely from it.
We can see both of these strategies at work today with Carl Goshen playing the role of the strong willed chief executive that has the vision and through pure will tries to force his company to follow him to the future, the whole time under fire from the media, the shareholders, the board, and his own employees. Unfortunately for him, I don't think he has the power to do it. It is an incredibly rare power. I think Elon could do it, Steve Jobs certainly could. I wish Goshen the best, but I don't know that success is one of the possible outcomes. On the other hand, we see Toyota and Daimler taking one of the easier routes by investing in a completely separate entity (Tesla). Though, both invested far too little and have recently pulled back or out of those investments and decided to address this new market from the within the main company (history says that won't end well).