I absolutely keep all of my ducks together. That choice is your decision to make, to keep them pure or let them in. Whatever it is, I'm sure your animals will be beautiful either way, as crossbreeds can be better than regular breeds at times.
He most definitely is a Rouen. I have Rouen, Blue Swedish, Black and White Magpie, White Pekin, Khaki Campbell, Fawn and White Runner, Black Runner, Snowy Mallard, and I'm trying Buff Pekin. I haven't tried crossbreeding yet, as I'm going on that journey this year with my Rouen drake, but many...