Not sure how you can say you got a great deal if it doesn't fit, this should be the #1 priority for any bike. That said, you can always make a small bike bigger, with stem & seatpost adjustment, just look at the stem length at the Giro this year, they are getting real long again. Would help if you gave some basic details about yourself, like your height, and what the bike shop suggested
For your questions,
1 - What bikes, the SST comes in 4 versions, so hard to compare when you don't know the specific one
2 - All frames have to undergo CEN (EU) / CPSC (US) testing, none are going to brake easily, if it did fail in a crash, it would be long after a steel or Alu frame would have.
3 - Nothing wrong with Tiagra, it's good entry level 10 speed, with the design / cosmeitcs of the previous generation of 105 (5600), if you are planning on upgrading, just buy the bike with it already on, it will be cheaper in the long run.
4 - Warranty, have you asked the bike shop? it's on their (Fuji) website
http://www.fujibikes.com/support
5 - Fit, Fit, Fit, think you may have got this by now.
Edit, just seen you have added your height, would go for the bike being too small, but still got to ask, why they didn't question this at the shop when you bought it?