I personally think that trying to convert a mandarin to eating other foods is not benificial to the fish, and will shorten it's life. Also seems to be a waste of money.
Simple money spent is on some rock rubble and create some pod piles. Target feed the pod piles for a month or two, and watch for explosions in your population of pods. After you notice that the pods are living/feeding in the piles, start feeding your tank phytoplankton and or DT's to feed the babies.
I have two very fat and healthy mandarin's in a 80 gallon tank with a 6" DSB and around 100 lbs of rock. I also have a midnight pygmy (nox) angel, a neon dottyback(until I can catch it), that also eat the pods with a strong appetite as well. I have a 29 gallon refugium hooked up to this tank with tons of macro algae, and you can see that I have a crazy amount of critters in there.
It took about 2 to 3 months to attain a healthy enough pod population before I introduced my first mandarin. I happened to find a great female (first one was a male), a week later, so I got that one as well. After months of this, I still have an amount of pods and critters in my tank, and refugium, that most people don't even have.
My vote is for YES on the mandarin, but only after proper preperation and research. Do a search on 'pod piles' to see how a couple people have done this. I feel you have a relatively small tank for a mandarin, but with the amount of rock you have, and the addition of pod piles, a single mandarin should do fine.
As with ALL the fish that we get, some unfortunately die. The mandarin family is not any different on that part. They are generally thought as hardy fish. And with the proper research and preperation, a lot of people could maintain a healthy mandarin in their reef tank.