Tallahassee is closer to Georgia and Alabama than it is the heart of Florida.
Florida State could add some National cache to the SEC, but they don't need it. It would hurt the ACC far more than it would benefit the SEC. They would much rather grab a team to fill the footprint of surrounding states. They'd take NC State 10 times out of 10 over Florida State. After that there's more questionability as to who they finish with (Virginia, WVU, OU). I'd bet they'd take OU and OK State before FSU.
You could easily be right about who they'd take ahead of FSU. But FSU is still Florida, no matter what the geography. I've been around south GA & Alabama, and they support their state teams (rabidly). I speak only from a recruiting perspective, so maybe you're talking a different angle (TV market?) but FSU's ballpark in all aspects is Florida, and the SEC absolutely covets that.
Yes, but FSU adds 0 new markets. Georgia, Auburn, Alabama, and Florida effectively cover every square inch of TV real estate that FSU touches. Adding Miami of FL would help add to the influence over the state of Florida far more than FSU would, but like I said, no one outside of the American would take Miami.
The only thing that matter in realignment is money. The biggest money factor is TV. FSU adds value in terms of huge match-ups, but it's not a problem the SEC has selling. The incremental ratings spikes FSU would add would be easily outpaced by adding new markets.