Thanks for the input, everyone! I will try the strategies from the Reptilink videos next time I attempt to feed and schedule a vet visit. Other than checking for parasites, is there anything else I should ask the vet to test for? It's helpful for me to know what to advocate for.
Interesting to hear that your middle-aged males eat like this as well! Mine is a little younger than middle-aged, but it's also possible he just needs less food now and I was overfeeding him without realizing it.
Glad to hear that his body condition is actually looking okay! Now I'm wondering if maybe he was more than a little overweight and over time I got used to how he looked so I didn't even realize he was getting too fat before. It's possible that he's now actually a healthier weight and I'm just not used to seeing him look like this.
I wish I'd kept better records of his weight over the past 2 years (I stopped weighing him regularly after he reached adult size) which probably would have tipped me off that the feeding was wrong if he was gaining weight despite being fully grown. I weighed him today and he is 1746 grams and I've been offering him ~50g small rats every ~14-18 days. Maybe it's time to cut back to one rat every ~21 days?