First of all, I would increase the number of barbs, danios and tetras. All of those fish can be nippy and larger schools (I'd say 8 of each) will decrease the chances of nippiness. :)
As to whether a betta will get along with your fish, it really depends on the betta. Some make amazing community fish; some are angry little murderers. What is your water like (ph, hardness)? A dwarf gourami may be a better option.
The activity levels of the danio may indeed stress the betta out at first, but heavy planting and some refuges like the Zoomed floating betta log would help. :)