All angels have their own personalities. Some pairs can be kept in a larger tank with other angels, others turn into psyco fish murderers. I have 2 pairs in a 65 with 3 unpaired angels, they get a little aggressive when spawning, but not much. I have other pairs that require their own tank, anything that looks like an angel gets torn up. It's a wait & see sort of thing. If you run into trouble, most lfs will be more than happy to take 1 or 2 fully grown angels off your hands. They are great sellers, a good money maker for any lfs.
The angels won't bother the adult livebearers, but I doubt you will see any fry. This is probably a good thing, as your parents will only let you have 1 tank for now. The fry are great food for the angels as well.
The barbs are your choice. I wouldn't take that chance. It would really suck to wake up one morning to what were fully grown show quality angels with a buzz cut, and no other tank to treat them in.
Tolak