Welcome to the boards! For future reference you should be able to find questions like this via the search bar up near the top of the page, or potentially in this very thread.
However, here's answers to your questions in case they haven't been answered here:
No, you can't have him give CGC the thumbs up that they're signed by him. A witness needs to be present at the time the book was signed.
If you submit the book as it is, it will get a green Qualified label saying that there's a name written on the cover.
If Neal signs the book again you will get a Signature Series/Qualified label, stating that the book was signed by Neal Adams but there's also a name written on the cover.