I would have pushed for the verbal, honestly, I think that is what a lot of coaches are doing now and I think it is kind of like sales in that regard, don't let them "think about it" and "get back to you"
Now, at the same time, it doesnt mean you are trying to force them but pressure is not a bad thing.
"Johnny, I have to tell you and I have to be honest, we do want you here at Nebraska, we think you will be a special part of this program with a very bright future but we also have to think of the team and the program first. You are who we want but if you are not thinking that Nebraska is the place for you, please, let us now, that way we can continue our search and you can look for the perfect fit for yourself, what do you say Johnny?"