Overstocked in my saltwater bio cube? Please help I give best answers.?

I have a 3 month old 29 gallon biocube with from 1/2 to 3 in of sand spread around the tank, shallow in the front deep in the back, decent water quality that is declining slowly I have to do more water changes recently to keep it up to check. I have a small snowflake eel about 10 in long, a baby maroon clownfish 1.5 in, a coral banded shrimp, four nassaurus like snails some small some huge, a big turbo snail, 3 small hermits, a baby horseshoe crab very small i will trade it in when he gets too big, a anemone, a tiger jawfish, and a small coral lke thing I can't identify. Everything is doing well and in 3 months, one thing has died. I had a BIG hermit that was found alll across my tank out of its shell in pieces i don't know how it died any ideas? I was planning on upgrading to a 75 for my snowflake in december but now feel like i don't want to it just sits in its cave and makes a huge mess. I could trade it in at my lfs along with my coral banded shrimp (the two most aggressive things in my tank) would this reduce the bioload massivley? I don't know if it is worth it to trade him in. If I did get rid of my shrimp and eel, could I get another maroon clown and try to breed them when they age then get a proper anemone I know they can host to? I want some colorful fish to swim around my tank it looks like poland in the 40s right now all depressing with just my clown occasionally swimming by then my eels head poking out into the water which is a bit cloudy and not clear? I love the eel but he is ruining my tank andI know he would be better off in some 100 gallon tank than in here. What should I add to my tank? read what I have in it again and tell me if it would be overstocked without the eel and shrimp and what kinds of cool colorful fish I could get to keep in the tank for at least months until I upgrade to a 55. there is quite a bit of swimming space as the clown is the only thing ever swimming about... please don't name boring fish like a blue damsel I want something that will be okin the tank for a while at least and swim around looking cool... Also should I add a bigger cleanup crew? Thanks so much if you took the time to read this I WILL give best answer