Welcome to TFF. Well, you have some serious issues with the present stocking that I will try to explain. Another matter is cycling, did you cycle this tank before adding the fish? I'll leave that and concentrate on the fish issues. And let me begin by saying you are not alone in what has happened; many of us started out the same, with the wrong combination of fish, but on forums like TFF you can get assistance.
The first thing is numbers. Some of the species listed are what we term shoaling fish (some call them schooling). These species need several of their own or they will be under stress and this leads to health issues, aggressiveness (increased in the case of naturally aggressive fish) and trouble long-term. Numbers can vary, and some species have minimums. In general terms, all tetras, barbs and corys are shoaling fish, and a minimum of six is recommended; more is always better, and you have space so I would consider that once we sort out the other problems.
However, you have a couple species mentioned that need more than the minimum. Tiger Barbs are one, with 10-12 being best. Albino TB are the same species, so they mix, but you still need more of them. This is a naturally aggressive species, prone to fin nip, and keeping a larger group can confine the nipping to within the group and even reduce that. But there is another problem with this fish's nipping tendency, and that is that it usually directs this at sedate fish, like angelfish. Barbs should never be combined with sedate fish, it is a recipe for trouble, like waving a red flag in front of a mad bull. The Black Widow Tetra is very similar to the Tiger Barb in its aggressive behaviours, so same advice holds.
I've no idea what the "Tripod Barb" might be. It may be OK, or may not. But being a barb, the same issue applies that it will be too active for sedate fish.
Given that you seem to be wanting more fish, I would suggest you return the barbs (albino and tiger) and black widows; maybe the Tripod too, depending what they are and what you decide to go forward with in general. The store should be willing to take them, given the circumstances, if they want your continued business.
The Polypterus senegalus must go back. This fish gets 12 inches, is very predatory, and is not going to work no matter what.
Molly. If you have fairly hard water, this fish will work from that aspect (it must have mineral in the water). Perhaps you could find out the specific GH (general hardness) from your municipal water authority, on their website; I will assume the store did not give you the actual GH number, and we need to know it. The GH is critical for all fish. Aside from this, being a livebearer, and if you have male/female, or if the female was impregnated before you acquired her, you will have fry by the hundreds for several months. This may seem nice, but what are you going to do with them?
Angelfish. This also is a shoaling fish living in smallish groups. But here we have other issues. It needs at least five in the group, because it is an aggressive fish by nature and establishes an hierarchy within the group. Males are very territorial. The two you have, if both males, will soon not get along if they are normal; two females is less of an issue. A pair will work, provided they have bonded, as they need to select each other.
The X-Ray Tetra I assume is Pristella, this is a nice fish, and depending what you decide on the problems, you could get another 6+ of this species. But please sort out the troubles first, as adding any new fish is only going to increase them.
Byron.