Ghost shrimp are only supposed to get to 1-1.5 inches. I am going to put in maybe a pygmy cory, a dwarf frog *still needs more research*, or a few tetras in my 5 gallon with my betta. But he is really curious so i think he would do fine. He loves to interact with things.
Bettas don't like current. I have an undergravel filter that seems like they don't mind, or i also have the kind that has a piece sticking down sucking up water (I am sure there is a better word for this) and it was to strong. So i put in a piece of sponge at the bottom. seem to do well...
Some fish like bubbles, others don't. One of my bettas LOVES his bubbles, the other one is just kinda "eh" about them. Good luck. I would write more but my mom is yelling for me to go... ttyl