Hi Caroline. Oh no, no such thing as too much information. I only wish all folks who ask about birds would understand that the more info. they provide, the better their answer is likely to be. I appreciate all the detail you provided. I can see that you are already well versed in your Budgie information. Therefore, I'm sure you also know that the more we get in to the color mutations and adding the factors like Opaline, etc., the less sure we are able to be of sexing by visuals. Very similar to the difficulties when we have Cockatiels of the many color variations. It's difficult to find information that will talk about Opalines and visually sexing, in the same article. Based on all the factors you describe, I have to lean towards the bird being male. Another thing to consider is the color mutation he may actually be. You describe him as "periwinkle". True periwinkle is generally a much light blue than the Cobalt. If he has had a true full molt, he may remain the lighter color. If he has not yet had it, he may darken a bit with the next one. I can't weigh in stongly on the age thing either, based on the molting. Having them in our climate controlled enviornments can sometimes wreak havoc on their biological timing, including everything from molts to hormones. These color mutation situations can be so tricky, not many folks, including me, who cannot see the bird with their own eyes, are going to stick out their neck and give a definite yes or no. I'm going to insert a couple links in here just in case they may have some additional information on the Opaline factor that you don't have yet.
Pet Advisor
Several yrs. exp. with all types of pets, specializing in parrot care and behavior.