Hi and welcome to you and Shadow!
To be honest, I didn‘t find the weight charts etc a lot of help, cockers vary so much, we have some on here reporting theirs are 11 kilos end weight whereas others can be 16/17 so its difficult to judge without seeing the dog. I do remember however that I nearly drove myself and the rest of the family round the bend fretting over Humphrey’s weight as a puppy and it spoilt the joy of puppyhood to some degree. The term „puppy fat“ is literally that and they very often look very chubby at that age but take on a more slender look as they mature. A more reliable guide is to feel the body, you should be able to feel the ribs and when viewing the body from above, you should be able to see a waist, although even then, my dog didn‘t develop a figure, as such, until he was a bit older.
His routine sounds good so as long as he‘s healthy and doesn’t feel „fat“ and is not getting too many extra treats, I wouldn‘t worry too much.