The reason it is said to wait longer to put an anemone in a tank is because of subtle changes your tank is going thru as it settles in. No big swings of nitrate, nitrite or ammonia but little things that mean your tank has really taken hold and settled in. This is not hard and fast, just a guidline and there have been people who put anemones in earlier and do fine. They are sensitive to water conditions...keep up with water changes. I have no doubt with a 28" zebra moray, you have a lot of waste in the tank...water changes are a must to eliminate the problem. Do your testing, keep your parameters as close to zero as possible.
As for feeding, I have never fed chunks of anything to my anemones...in the wild, they very rarely catch any large pieces of fish, shrimp etc. In home tanks they catch more fish than they would in the wild...it's cause a tank is so much smaller. The clown hosting in them may bring pieces of food back to feed it (mine do) but again, they are small pieces. If it needs more light, it will move on it's own, until if finds a spot with lighting and flow that makes it happy.
If you notice it losing its grip, mouth always gaping, its tentacles losing their stick, keep a close eye on it...if it dies in the tank it can foul things up pretty bad.
Also, if you have powerhead in the tank for flow, make sure there is something like a sponge or grate covering the intake as anemones and powerheads don't mix.
Good luck.