If you read the thread that matlee made about keith, his oscar would not tolerate large tankmates and would only be happy with small ones.
It all depends on each individual.
You can have a mental JD who's a serial killer or you can have an oscar who will tolerate tankmates well.
It would not be overstocked but would be badly stocked, If I was you I would up the tetras to about 6-7 and forget the danios, add the mollies and maybe a dg.
10 Gallons isn't really big enough tbh.
Depends on the upgrade you get, a couple of rams will work with a bristlenose, ottos need to be in groups and need to be in tank at least 6 months mature IMO.
Are you sure on tigers and gourami's? Im pretty sure tigers will rip out their feelers and tear them up, also the same with the cories.
Rehome the electric yellows.
Yes a Jack could possibly work but then again it might not.
Your best bet would be a severum, great tank mates for oscars!
What about another type of species?
Like an oddball?