All very valid reasons. Let me examine each of the points you made with my own response:
1) Indeed, TB is close to being a Cup winner. But for this to happen, they'll need all of their current nucleus. If Stamkos re-signs with them, this means they'll have to say goodbye to several players among this current nucleus, players such as Hedman, Kucherov, Johnson and Bishop. They won't be able to re-sign all of those players if Stamkos re-signs. And Hedman, Bishop and possibly Kucherov are as important to the team's success as Stamkos is. Plus Stamkos is now a financial risk considering his blood clotting problems may come back to haunt him and whomever team signs him. Big risk.
2) Indeed, it's the only organization he's ever known. But some of his family members have been telling a friend of mine living in Toronto over the past 3 years that Stamkos' wish from the moment he entered the NHL was to one day play for his hometown team, a team he idolized as a child: the Toronto Maple Leafs. His window of opportunity will never be as great as it is now to fullfill his lifelong dream. There is no way he will now accept a so-called 'hometown' discount after rejecting an 8 year/$68 million final offer from the team a few months ago. Plus the fact 'hometown' discounts simply do not exist in today's NHL. The NHLPA would never allow one of its members to do so (and has warned players and their agents behind closed doors about this) since it would keep player salaries down instead of rising. Stamkos also has a problem with coach John Cooper, who was given an extension at the end of last season and isn't going anywhere.
3) Much better weather than anywhere else. Really? Much better than Arizona or California? Maybe Stamkos doesn't care that much about the weather. Maybe he'd rather play in a major hockey market and Toronto is the #1 hockey market on the planet. He'll also get to visit Florida, Arizona and California during the NHL season. Plus he's single and nothing is holding him back from leaving Tampa. Maybe he'd prefer spending an entire year living among his family and friends, although he did buy his parents a condo in Tampa a year or so ago.
4) True, there is no state income tax to pay in Florida. But there are other ways to escape higher taxes in Canada when you're an athlete or a celebrity. It's too long to explain. And he certainly could recoup that amount from the large number of endorsements he'd get playing in Toronto. And who knows, maybe money isn't that important to him as it is to most of us. The fact he refused $68 million from Tampa (average salary of $8.5 million) flat out possibly proves this.
5) Stamkos has likely already met Esposito since Trader Phil works on the team's radio broadcasts. Esposito would be a hypocrite to tell him he can bleed only one color since Esposito has bled many colors throughout his playing and executive career.
I say there isn't a chance in hell Stamkos re-signs with Tampa. It no longer makes sense for the team, and he's had his mind set on Toronto ever since he entered the league. The only reason he won't sign with the Leafs will be because the timing wouldn't be right at this time for them to sign him. Plus the risks involved. But i say that Toronto is the current odds-on-favorite to land Stamkos.