Hahaha nice video! When you dropped the camera into the water, I did a little double take here. "Wait...what? What did he just do??" Very cool, and now I'm going to go searching for waterproof cases for a Galaxy S3. LOL.
In terms of suggestions, I suppose my pointers would depend on what you want to do with this tank. I'm going to assume FOWLR since you have that beautiful angel and puffer....you're not going to be able to keep many corals or invertebrates with those in there.
First, I agree with the esteemed Mr. Sweater. I know you think there's enough rock, but remember.....live rock is still one of the most efficient biofilters we have, and it's beneficial for the fish in so many ways. You mentioned that you don't want the tank to look overstocked when the fish grow out. It won't, trust me. In fact, if you add more rock and keep an open plan (caves, holes, etc), the fish will make full use of the new hiding spots and will be healthier for it. Right now there's a whole lotta open area. This is cool from our point of view, but it means that a certain number of fish have to compete for a finite number of "hidey holes" in the rock. This is especially true at night, when (in natural reefs around the world) reef fish tend to find a hidden nook or cranny to hunker down in and wait out the nighttime predators.Even though there AREN'T any predators in your tank, the instinct to hide is still strong and will cause the fish stress if they can't find a spot.
I understand if you want to avoid the "pile of rock" look in your tank. Personally I built upwards with columns, and you could also try your hand at adding large rock and mastic them together to form miniature coral bommies for the tank. Two bommies, with a few smaller rocks surrounding the main structures (maybe something bridging between them??) would look VERY cool and original in a tank like yours.
Second, I have to tell you that there's NO such thing as too much flow in most saltwater tanks. There are exceptions to this, but a 135g FOWLR isn't one of them. The more flow, the more gas exchange, and the less chance fish poop has to settle. I'd go with a few big Koralias in there easily....maybe even a WP40 or two.
You didn't mention much about your filtration beyond the skimmer and carbon, and I have to say I noticed a lot of particulate matter floating in the tank. I understand this because I battle it often as well. I think you need a better prefilter to polish the water up a bit. Either a filter sock or a few sheets of filter floss. This has to be changed pretty often, at the bare minimum once a week. Socks can be washed, and filter floss is cheap.
I also noticed some algae growing on the back glass. If you can source Atlantic Grazer snails for a good price, I would keep a good number of them in the tank. You're going to have to replenish them every 6 months or so, because the puffer is going to see these as a nice snack from time to time. Nothing you can do about that, but they are very effective at removing film algae, and if they're cheap, then they sort of serve a dual purpose....cleaning crew, and occasional light snack. Who knew Escargot could be so beneficial??
Anyway, those are my shoot-from-the-hip comments. I'd love to hear more about your tank!