1) Yes (and arguable)
2) The only ships you can use that skin is on the T5 Galaxy Retrofit and Galaxy Dreadnought.
3) No, you have to buy the Galaxy Retrofit ... only thing you get is the console and the skin.
You start your career off as a simple farmer... then you launch yourself into a galaxy filled with intrigue, power plays, and high stakes games of interstellar conflict, as your career careens upwards onto your final destination ... a level capped Dilithium and Fleet Mark Farmer!
No, you're not missing anything. Yes, it makes very little sense to buy any ship but a level 50 one.
Of course there are people who take weeks to go from level 30 to 40. Not every player is a power-gamer trying to get to 50 ASAP. Plus you have access to the Console from the Venture purchase at all later levels and on all ships. And, as was said above, a huge percentage of the player-base has multiple characters so that ship can be useful for many months when spread out over a dozen, or more, characters that player might have over the years.
STO is about my Liberated Borg Federation Captain with his Breen 1st Officer, Jem'Hadar Tactical Officer, Liberated Borg Engineering Officer, Android Ops Officer, Photonic Science Officer, Gorn Science Officer, and Reman Medical Officer jumping into their Jem'Hadar Carrier and flying off to do missions for the new Romulan Empire. But for some players allowing a T5 Connie to be used breaks the canon in the game.
What about the Fleet Corsair Flight Deck Retrofit. It takes 4 Fleet Ship Modules. Wouldn't it be better for me to Corsair Flight Deck for 1500 Zen then only have to buy 1 Fleet Ship Module for the Fleet version. Correct me if I'm wrong on this one, but it seems like the same price for 2 ships instead of just 1.