See when you have under a couple hundred teens onboard and an autism program running simultaneously accounting for more than half of them, you are left with less than a hundred "potential" teens for the program. Take off the amount of teens that idle with their parents and the ones that are only there for the cruise itself and not the teen program and you're dwindling your number.
Another explanation is that you disembark the day before the presidential inauguration. I'm pretty sure anyone who is off school is headed to Washington this weekend to be there for it. So combine that with the offseason, the autism group, and the relative shortness of the cruise itself, and I think you have a pretty solid explanation for the tumbleweed blowing around the teen club.
As for the time change, I do recall Cozumel (your next port) falling an hour behind EST during the winter, although I could be wrong.
And that cable suspension bridge is always fun to go under. Went under it on the CCL Inspiration and the smokestack barely cleared. I do believe its an hour or two from the Port of Tampa.
Sorry your last cruise as a teen was ruined though. Hoping it gets better for you