Wow. This was a very stressful read. I say this with nothing but the desire to help.... SLOW DOWN!!!!!
There are a lot of topics on this thread, so let me just throw some stuff out there. First and most important. How is it possible to do research and still decide that you are going to use bioballs??? This is simply not acceptable. You can't make this decision. You are going to completely ruin your marine fishkeeping experience before you ever buy a fish. We will have failed you miserably if you decide to use biomedia. You may as well buy some liquid Nitrate and dose it daily to your aquarium. You want a deep sand bed, live rock, and the best protein skimmer your wallet can afford. No biomedia. Period. Please explain your decision so that we can discuss further.
When it comes to compatability, you will get different opinions. Why? The order in which fish are added, the tank size, the aquascapping, and the total bioload all play a huge impact on how fish behave in an aquarium. It is a very difficult task to really determine what mixes together well inside a small glass box. However, i can tell you this... it is more important to ask yourself "HOW LONG can these fish to live together?"
In your situation, I would personally feel comfortable putting any LARGE clownfish with a Dwarf Lion. The nice thing about Lionfish is that they are almost never the target of aggression, and they are NOT an aggressive fish. They are a predator and will eat anything that fits in their mouth, but they are not territorial at all. They are one of the rare fish that you can easily determine the chance of compatablity success.
When looking at other fish mixes, think about color and Family / Genus. If 2 fish are of the same Genus, then they will probably not get along in a 90 gallon tank. If 2 fish are of the same FAMILY and same color, then they will probably not get along. For example, a Coral Beauty Angel and a Koran Angel will typically get along fine together. But you would not put a Coral Beauty with a Lemon Peel Angel, both of the Centropyge Genus. You would also not mix a Yellow Tang with a Lemon Tang, both from the same Family.
There are a few exceptions, especially when you keep fish in pairs. Clownfish fall into this category and usually will do ok in a pair. It is generally not a good idea to keep different species together, but this is a loose rule of thumb and seems to work 20-30% of the time with some degree of success. However, the chance of failure is high enough that it is ill advised.
I think your fish list is fine. A LARGE Maroon Clown, Snowflake Eel, and Dwarf Lionfish should be fine. You could add your choice of Zebrasoma genus of Tang, and still have room for a couple other selectios.
On the subject of UV.... YES YES YES YES YES!!!! They are not expensive and can be a lifesaver!