Looks good! I have a tiny yellow clown goby in my picotope with sexy shrimp and it's great. Check the adult size on the clown gobies - they can be very different. I like the pandas. Sexies should probably be well fed with zoas in there too though. A peppermint would be nice. I threw 2 skunk cleaners in my nuvo 16 and they seem WAY too big. One maybe, but they are extremely active. I couldn't imagine one in my 3 gallon.
I use a 16 ounce or so cup and just dip it in the tank to do water changes once or twice a week. I probably aim for about a half gallon a week. A Rio 50 might be worth a try in there. I have one and keep debating adding it, but everything seems happy now so I keep waiting. It would be perfect flow and you could aim the nozzle behind the rock. I don't really use carbon unless I have the need. I just stuff some filter floss in the little hob and change it out a couple times a week.
I find that with the picos, keeping it simple and using primarily water changes and a little mechanical filtration works best.