A volitan lion will get awful big for an 80 gallon tank, but a 125 would suffice. A 125 is the smallest size tank I would put one in for long term, but it will work. Otherwise I think your original fish list will work fine, but I would also recommend getting one eel. You will also have to watch the niger trigger with the lion. Sometimes triggers will nip lions fins, but if you keep water quality good through consistant water changes and feed well I dont think you will have any problems. Especially if you buy all your fish as juveniles and let them grow together.
A wet dry should work on the tank as long as you have enough flow in the tank and through the sump. You will also want to do about 20-25 gallon water changes every 2 weeks with premixed salt/RO water. That will help keep the nurtients down some.
A skimmer is always good to have, but if you buy all smaller fish and let them grow into the tank then you shouldn't have any problems waiting a few months to get a skimmer. Smaller fish won't put off nearly as much waste. Don't waste your money on any of the cheap skimmers like a seaclone or prizm, etc. Save until you can get a good one that will actually make a difference on the tank.