Hello. I don't have time to calculate stocking right now, but I will quickly talk about compatability.
You have to be very careful with gouramis. 3spot, Opaline, and Gold Gouramis are Trichogaster trichopterus, and they can be very, very aggressive, especially males. Some people describe these as "hit or miss", because many of them have an aggressive temperment and will destroy any fish around. This species can wipe out a community if it chooses. Use extreme caution if you decide to get any one of these Gouramis. Inspect all fish regularly for fin rips or damaged places (these are common with some Trichogaster tanks, these injuries can quickly lead to infection).
I would definately not recomend that you stock these with Pearl Gouramis, as they are fragile and much less aggressive. I also would not recomend stocking Zebra Danios with any Gourami, reguardless of species, as Gouramis are slow-moving and will become stressed by the hyperactive Danios.
Corydoras are generally Ok and left alone by many other species of fish. In larger tanks I like to see these guys in larger groups, as they are a shoaling species. As with any shoaling species, the minimum number is *bare* minimum (bare min for corydoras is 4), but they will flourish more effectively in larger groups, just as long as it isn't effecting the water quality.
Black Skirt Tetras look great in groups of 7 or 8. These are one of the largest species of Tetra (behind Bleeding Heart and afew others), making them less likely to be assalted by an angry Gourami. Still, you have to use extreme caution.
So maybe that will give you something to think about and plan with. I hope this helps.