I've moved your post over here to the CC forum as you will get more answers on the AU reporting question.
As for FICO 08, it will count AU in scoring. However, it is very important that you not rely solely on AU accounts for your score, and consider adding some of your own, either now or later when your credit has improved(if that is what you are waiting on).
Your status as AU will be affected (presumably positively) as soon as the creditor reports. More than your partners overall score, you want to be certain the accounts you are the AU on report a low utility and no lates.
I am currently authorized user on few of my wife's accounts. Since now I have cards of my own, and the fico factor also does not consider authorized users, i am planning to remove myself from all such accounts of my wife. Could you tell usually how long it takes to remove this information from each of the 3 Credit Reporting agencies.