Did Harry originally intend for Veronica to sell his criminal notebook
Maybe yes maybe no.
At the end of the movie, Harry say to Veronica :
It's meant to be simple. Why couldn't you just sell the book to Jamal
and come to no further harm?
I'm not sure about this.
Anyway I think Harry will further harm her in such condition:
Harry rob Jamal 2 Million USD
It seems the deal with Mulligan after Harry rob Jamal 2 Million,
Harry will give Mulligan 1 Million, as in the boat Mulligan say to Harry :
I want the full amount, Harry. One Million, like we agreed.
I want that money. If not, you're gonna be alive again
So that means, Harry has not give full 1 Million to Mulligan.
Then Harry say to Mulligan:
I can get your money, but I need time.
This part is quite confusing to me, because it raise a question :
Why Harry need time ? Why didn't Harry just give the 1 million full to Mulligan while Harry has the other 1 million for himself alone?
So I think at this point, Harry didn't care at all of Veronica that she rob the 5 million from Mulligan.
Harry deliberately use Veronica to do the robbery, hoping his wife will succeed, then he plan to rob his wife (kill his wife if necessary) the 5 million and pay Mulligan full one million.
So, back to your first question...
What he said to Veronica maybe it's just a lip-service to her, because even if Veronica sell the book to Jamal, say for 1 million (because Jamal will get 5 million if he succeed the robbery on Mulligan's money) - Harry will rob that 1 million from Veronica to pay Mulligan.