First of all, you don't need to get annoyed when people "attack you" about stocking. If you joined this website then you clearly want to get advice from others and that is a good sign as it means you care about your fish. If people ever tell you that your tank is overstocked though, and you shouldn't get any more fish, then you should really take their advice, because I can bet my bottom dollar they'll be right.
Also, even though Aqadvisor says that doesn't necessarily make it correct - and the site acknowledges that when it says this as a footnote at the bottom of the site:
"We highly recommend you to do further research, discuss results on your favorite aquarium forums and websites. Your favorite aquarium forums won't necessarily endorse or agree with the recommendations reported by AqAdvisor.com. Use AqAdvisor.com to get general stocking recommendations but do your own research BEFORE buying any species. We highly recomend that new tropical fish keepers understock (less than 100%) their aquarium tanks."
But anyway, in this case, you probably could add another couple of smaller fish. I'd go for 1-3 small livebearers such as guppies or swordtails if I were you. Or you could go down the shrimp route, but that could be risky with the fish you chose. Your tank sounds like it will provide some good hiding places for the shrimp though so it could work, but beware that others may advise against it.
Good luck!