Even though the dwarf fuzzy maxes out at 6", 4" is a much more common length in the home aquarium. The fu manchu is about the same size wise. The only reason I would even suggest them for a smaller tank is that these are not very active fish at all. Most of their time is spent perching on the rock, sand or in caves. Actually, they can be rather boring in a tank by themselves as they don't do much! They also have much smaller pectoral fins than the larger lions, so turning around is not a problem in these smaller tanks. If we were talking about tangs, then this would be a different story, but again, these fish are not very active. Keeping the wastes down to a minimum comes with good tank hygiene and not overfeeding the fish. Since Bubbagump is keeping oscars, I'm sure he understands about tank maintance and messy fish!
If you decide not to go with the lionfish Bubbagump, then the tomato clown, and scooter blenny will be fine in a 20g. The flame angel is iffy IMHO because not only are they rather delicate, but they require a mature tank to do really well. (BTW a mature tank in saltwater is one that not only has cycled but has been up and running for at least 6 months to let everything "balance") Also the flame added to the other fish, and you're back to the 29g!
HTH