1) I wouldn't worry about the hardness of your water. While it is high, it's on the low end of what is considered high. It should be fine. Most Tetras are actually soft water, that doesn't mean you can't have them.
2) A bag of water from the pet shop isn't going to do much, if anything to add bacteria to your filter. Some fish shops float bio-balls or other media in their tanks and sell them. This would be a better source of bacteria to seed your tank. Another option is to ask for a scoop of gravel, or media from their filter. This can be done the same day you get your fish.
3) Don't worry about the salinity, not enough to make a difference.
4) UGF is not the best option for a filter. I used to have them, and they worked OK. They canand do cause problems long term. A hang on power filter is really the easiest, least expensive type of filter IMO.
5) As far as fish that will "do better" , Brackish water comes to mind as do African Cichlids. Brackish like both salt and hardness, Rift lake Cichlids do well with the hardness and the salt wont be noticeable as said previously.
6) You should be fine with most fish except the more fragile ones like Discus for one. Fancy tailed Guppies, Platies, mollies (actually a brackish fish), and most livebearers are forgiving and easy.