I guess you were wondering about my signature (I just copied that from someone, its maybe not updated XD)
To answer some of your questions.
When your I-130 petition is finally approved, the service center that processed your petition, will send you another Notice of Action letter indicating your approval, and the forwarding of your approved petition to the National Visa Center (NVC) in Portsmouth, New Hampshire, along with a phone number to contact the NVC with. Your case will now only be dealt with by the NVC. The service center that you filed with, will have no more knowledge on the status of your petition or case.
A few weeks after you have received your last Notice of Action indicating the approval and forwarding of your I-130 application to the NVC, the NVC will send your relative a packet of forms that you and your relative must fill out before your relative can be given an interview date with a consulate abroad. The packet will likely contain instructions to fill out the DS-261 and DS-260 online forms, by the intending immigrant. An I-864 form is also included that must be filled out by the petitioner (living in the US). The I-864 is the Affidavit of Support form that requires copies of the petitioners past 3 U.S tax returns (or tax transcripts which are free from the IRS) as well as any bank or financial records available (see the I-864 for exact requirements based on your case). The petitioner must make at least 125% above the U.S federal poverty to indicate to the U.S government that the intending immigrant will not become a federal charge to the government when he/she arrives in the U.S.. If the petitioner cannot meet these requirements, then he/she must still file an I-864, and find a joint sponsor who can meet the requirements on his/her own. When a joint sponsor is needed ,proof of their U.S citizenship or permanent residency is required. (i.e. copy of birth certificate, immigration status etc). The joint sponsor must be residing in the U.S, and he/she must also submit his/her past 3 years U.S tax returns along with bank or any other financial records available. The joint sponsor must submit his/her own I-864 form to accompany the petitioner's I-864 form.
3: Can't find AOS exact fee but found the IV fee for I-130 is $325
And maybe this link can be useful for other questions. The fee is not updated though. I myself what to know the exact amount for 2019.