How can I expect this progression to go because I am so scared of the future.

I was told by the doctor it takes 4 years on average from diagnosis to it being terminal, and that it would appear to progress in stages with pauses between them.

The last two years have been denial (including continued efforts to regain their drivers' license) and we've just now hit the point where he has realized his diminished capacity (math and mechanical aptitude are basically shot now, memory is still OK) and actually used the word 'dementia' yesterday when talking about his health.

I've seen it worse, though. There have been a couple of injury-induced periods of delirium, which involved a blending of fantasy and reality, frustration due to confusion, and one incident of assaulting a nurse. I expect this will happen again in the next couple of years as the dementia progresses and there's no need for an injury to induce the state.

I'm told by a friend who has gone through this with a family member that the angry/confused/violent stage passes and there's some peace before the person dies, so at least your last memories of the person don't necessarily have to be something from a horror movie.

At some point there will be a need for frequent care. Family can only do so much for so long before they start to break under the strain, but professional care is expensive. We are currently dealing with problems with mental decline resulting in not following doctor's orders (and resistance to being guided into doing so), which of course accelerates the progression.

The expense of full time care will quickly eat through whatever money is available unless the patient has fantastic insurance or a wealthy family. My in-laws haven't realized it yet, but they're going to lose their home in the next year or two to pay for nursing care.

I'm not finding much in the way of treatment for vascular dementia.

That's because there generally isn't any. I highly recommend finding an alzheimer's/dementia support group and going to some meetings. It might just save your mind.