What an adorable little mug! The transition is pretty striking.
IRN def can have crazy and fast molts. I feed my little one (he is a plumhead - similar to IRN) some hemp seed during a molt too, seems like you have the right idea!
In terms of kale, I may suggest transitioning him to a chard, I use silverbeet - in US English it is called Swiss chard. If you are cooking the kale it is another story, but raw it can be hazardous if eaten too often/ too much. You are trying to avoid is too much
glucosinolate, a little isn't as much of a worry- but an everyday diet it can add up. Keep in mind that cooking the veggies denatures this. It is in
Kale along with other plants in the cabbage family. I will post this article for your reference.
www.sciencedirect.com