That depends on the mutations, doesn't it? The key point is that after thousands of generations, numerous mutations have been favorably selected, and have spread through the population. Others have been de-selected (by early death or reproductive failure) and have been removed from the population. The gene pool (that's the ball to keep your eye on) is then different from what it once had been. It changes every generation, somewhat, but over a great many generations the changes are cumulative. The creatures in the breeding population never notice this, because from one generation to the next, the effect is minimal. It's mostly apparent only when an ancestral fossil is found and compared to the current version.
It can also become apparent if the population is divided, perhaps by a river or something, and each takes it's genetic material and goes a separate way. In time (again, we're talking about thousands of generations) the two populations -- if they were reunited -- probably won't be one breeding population any more.
The mutation rate I used was from the figure you quoted of "one mutation per locus per 10^5 to 10^6 gametes". The figure for the number of genes in a typical mammal I used the number of genes in humans. I believe it is somewhere in the tens of thousands.
I must point out that your process has neglected to consider the negative probabilities of a changing natural selection pressures. As this is a well known phenomenon, it must be accounted for.
A changing environment does not affect the number of mutations that occur over time. All I have estimated is the number of mutations within genes that would be expected to occur over 1,000,000 years in a population of 1,000 mammals with a generation time of one year. The value is about 10 million. I do not have the expertise to go further and apply population genetics equations to figure out the proportion of those mutations that would fix. Neither do I know good estimate figures of the proportion of mutation that are harmful, or the proportion that are neutral or beneficial.
Additionally, I must also ask how many mutations are required for one species to evolve into another completely different species.
I have no idea how many specific mutations it would take. It would likely be different depending on the species involved. But I do not think the question should be how many mutations leads to speciation. Whether or not a change represents speciation is irrelevant to the probability of it occuring in a given time.
There are lots of books and web resources on the topic. Don't reinvent the wheel. Enjoy!