I am unsure what "next level" you seek. Your casting ability, as you describe it, is better than most people I know.
I can recommend a couple of things:
1) Create or find some overhanging obstacles and learn to cast under them. I can put a fly about 6 to 10 feet under branches that are less than 2 feet off the water. (although not EVERY cast) It's caught me plenty of fish that wouldn't "come out" to get it.
2) Learn to roll cast farther distances.
3) Learn to hook cast left and right ... putting a fly behind obstructions to "out of sight" targets.
A good suggestion, above ... look into competitions. I've not seen any, but I know they exist somewhere.
3)
I agree with Mike. You have plenty of distance.
There is pure distance casting, but for actual fishing, the ability to place slack and curves exactly where they are needed will get you more fish in difficult conditions.
There is also a difference between a true curve cast and and an underpowered curve cast. The easiest way I can explain it is that a curve cast can hit a target that is behind an obstruction. In the fly fishing masters competition a floating hoop was placed BEHIND a wall. The target hoop CANNOT be seen by the caster since it is behind the obstruction. The caster has to walk to the side to see behind the wall to locate the target and then walk back to the casting position to make the cast.
A true curve cast can curve the leader/line around the edge of the wall and place a fly into the hoop. For right handers, a left curve is easy but try to make a true 90 degree right curve is very difficult. Steve Rajeff did both on the fly fishing masters.
Most anglers will make a side arm overpowered hook. So a right handed overpowered hook will curve left around the wall. However the opposite underpowered cast that land in a right curve is essentially a side arm cast that collapses before it fully extends. The line falls in a right curve BUT it cannot curve around an object so it is not a true curve cast that can hook around the wall.
The ability to perform an accurate tuck cast for example is a cast that 99% of fly fishers cannot do in my opinion although it is a cast that is often referred to in nymphing books. How about a puddle or pile cast. Can you place all the slack into the leader and land the fly on target? How about a pendulum cast or a climbing hook cast which are parts of the shadow cast.
the Shadow Cast – the limp cobra
So there is casting for fishing and there is casting for distance. Casting for fishing is not about distance but about the ability to cast around and under obstructions and placing slack with accuracy.