Yes, only God can create Souls, but the plants and animals ritually created are fertiles because the essential nature of them includes that, i think. I think that should work.
Yes, they are fertile; when a thing is created by a Momentary Creo Ritual, it is from that point on a natural example of that thing, and follow all the normal rules.
In fact, even if you used non-ritual Creo magic, your peppercorns would be fertile until the spell end, at which point their offspring would disappear with their parent.
It is Rego magic (see p.78) that creates sterile fruit if it is used to force a tree to bear fruit, since Rego magic cannot create new things.