It's not a bad calculator - it's a good starting point, but definitely not the be-all and end-all of stocking. For instance, it doesn't take into account the shape of your tank, how heavily planted it is, and sometimes has some odd ideas on the bioloads of certain species. Definitely don't pay attention to its water change suggestions.
I would suggest dropping one of the glowlights to have a school of six, or, better yet, getting ember tetras, which are smaller (thus, smaller bioload) and get on well with bettas, in my experience. I'd also suggest replacing the cories with pandas, which are smaller, or pygmies, which are tiny. 1 or 2 25-30% changes would be fine. :)