So I'm kind of concerned about my beardie's weight. According to my scales he weighs 548g, but he is only 18.8 inches long. I have him on a diet of threes. Day one 15-ish gut fed locusts, day two salad, day three nothing, and repeat. I read here that you should feed them like this, but I have my doubts about this being an appropriate method.
I'm just a bit unsure how he can weight this but be shorter than average. Am I feeding him wrong or is there something else?
He looks like he's a healthy weight to me based on those photos. The method you're using is pretty good. It's similar to what I've read on some zoo based care sheets. As an adult the bugs should be limited. I usually suggest a bug meal 2-3 days per week. I like to offer a fresh salad every day and let them pick at it. The veges will provide nutrition but aren't very high in fat so I just let them self regulate that portion of the diet. That works out to being pretty close to what you're doing. I'd continue to monitor and log his weight because weight trends are a good indicator of overall health.
Scales are probably fine. 548g for a nearly 19'' dragon is pretty good in my opinion. A lot of it depends on how they're built though so it's important to look at the fat deposits on the top of the head and at the base of the tail to ensure those are filled in and to look at the arms and legs to ensure those are nice and filled in. Some dragons are skinnier than others too and that's OK, just like with people. You don't want to see them dragging their bellies on the ground, that's too fat, and you don't want them to be very skinny with bones showing and depleted fat pads, that's too skinny. As I mentioned, watch the trends. If he holds pretty close to that weight he's probably in good shape.
I offer salads daily and just change up what's in them based on what is available at the store each week. Offering the variety is healthy and since veges are low in fat I just offer it and let them take what they want. There are good options for salad items here http://www.beautifuldragons.com/Nutrition.html