A few suggestions:
1. I would avoid a Betta with an angel. Bettas like to beat up on any fish with longer flowing fins. it might work but you may still have problems.
2. Tetras work great with angels. you should be fine. get a few because they like to school.
3. to improve the overall health of your fish i always recommend adding some salt to your tank. you can get some freshwater salt at the pet store or you can go to a hardware store and get some Solar Salt (the same stuff used in water softeners). add 1 tbsp per 5 gal of water. this helps the fish build their natural
slime coat and will help you avoid most diseases including the dreaded ick.
4. While many people recommend additives to remove chlorine... I do not. the simple act of adding the water to your tank (esp if you have an areator) will evaporate most (70-80%) of the chlorine in the water. the rest will go out through simple filtration overnight. I have discus in my setup and i use tap all the time.
just my .04
