1. In terms of differences between BB and fighters like SF, you have what are basically "airdasher" mechanics like double jumps, air dashing, rolling on wakeup, etc. It is much more mobile, but there are still footsies. It just changes how you go about it. Other differences is how unique each character is, rather than having 20 characters that are basically the same thing except for 1 move being different.
2. There's a tier list, although I haven't looked at it for a while because the game is pretty balanced. You can do great with everyone. Some are better than others but it isn't anything extra work can't fix.
3. I use the 360 pad. It works fine for me, although I have to replace them a lot and then you get into each pad being worn out a different way so then you have to adjust all over again to each pad.
4. They are just for style points. Well, there is also a practical purpose: you can use them when the opponent is around 30% life or less. That means you can end the match instantly if you hit them at 30% so they have no chance to make a comeback. Usually that involves comboing into it.
5. The frame data is here on the Dustloop Wiki: http://www.dustloop.com/wiki/index.php?title=Frame_Data_(BBCSE)
6. Instant blocking shaves off some of the the blockstun you have when you block a move. It lets you recover faster, sometimes opening up a gap in the opponent's attacks that let you punch out or punish their moves. You instant block by blocking at the very last second. It also gives you a little meter.
Fatal Counters are moves with special properties on counter hit (Fatal) that basically make them ideal for punishing. If you land one, they will be stunned a lot longer and let you do a more damaging combo.