This question not only makes you think about the temperature, pressure but also the impact of gravity. Not moving away from topic, I must say that the region you are saying about is quite large in the view of metrics but quite short again if we really sense gravity.
The distance of a planet from the sun is maintained by gravity, but we must also not forget that distance between two planets is also controlled by the same. You must appreciate gravity because most of the features on earth are because of the same thing.
Now, if you want to calculate it more precisely you should know each and every postulates, theorems and properties shown by the space in nourishing our Earth for habitability.
Perturbation may give you an idea of adjustments, that how our earth is adjusting day by day for its decreasing distance from sun or increasing size of the sun. Talking according to theory of perturbation there may be more than 2-3 planets in the habitable zone. But still you cannot annoy the word "more" in that.
It shall depend mainly on the following factors : -
- Size of Planets
- Distance between each of them
- Distance from sun accordingly
- Their mass (priorly)
- Speed of revolution around sun
I know this information is not much for your question but this is enough according to recent knowledge about space. We even don't know the drastic changes happening in the space....the dimensions of space or how vast it is....whether it is measurable or not.....and if yes then are the measurements precise. Each answer tackles you more to have questions....But don't stop, just keep asking!