"would the formats with the highest results (2400 & 3600) ALSO include all the results in the lower number formats?"
The search volume information provided is Local Monthly Searches based on Exact Match. You can read more about Exact Match here: http://support.google.com/adwords/answer/2497825?hl=en
"In cases where you want to mention the state, would presenting it like this be harmful?"
Each time you add a new term to a title tag, you are increasing the page's relevancy to the new keyword at the cost of decreasing it to the previous keyword. Let's enter the theoretical world where all things are equal:
Title 1 - Homes for rent in orlando
Title 2 - Homes for rent in orlando fl
Title 3 - Homes for rent in orlando fl | florida
The problem with the 3rd option is it would never result in an exact match, which is the strongest relevancy boost possible. Personally, I cannot think of a scenario where I would ever use such a format.
All things being equal, if a user search for "homes for rent in orlando" then the first title wins (i.e. ranks highest). If a user searches for "homes for rent in orlando fl" then the second title wins.
The reality is this keyword is so competitive that anything short of a perfect match is not likely to get you in to the top 5 results.
Homes.com, Trulia.com, craigslist.org, Realtor.com, rentals.com, ForRent.com, etc. These are the sites which rank for the term. In fact, if you don't break the top 3 results, then the local results push you so far down the page, you might as well not exist.
When optimizing a title tag, the approach I take is to think as if I needed to rank #1 for the term. Once you achieve that goal, you can change your strategy and diversify. Until then...eye of the tiger.
