These larger species take longer to fully wean and would get support feeds from parents for a few more months I think without looking it up.
Food equals security. And they are much more likely to explore new foods after a feeding. Weaning by abundance. I would offer the formula in the morning then right after set out your fresh veggies and leafy greens . Babies tend to like them chopped up to around pea size st first. Increase size with their confidence and ability. And offer the pellets dampened so they are a little soft and crumble. They learn from their flock , do spend some time playing with the food with him . Offer the formula at other times and allow him to reject it take less as he wants . Usually morning and evenings are the last to be dropped.
Have a digital kitchen scale and weigh the bird daily in the morning and log .
This age in a bird your size , still needs a lot of extra guidance and support and contact to be a more confident and independent bird with less behavior issues as an full adult. They would be a sponge learning from parents and older siblings for the first year . Start working in foraging, very simple and done together at first . Foraging will fantastic way to keep that brain occupied down the road