Hi, let's go. I just had my interview in march this year:
1. Your fiancé is brazilian, right? If so I assume all his documents are in portuguese and if so, NO translation at all is necessary for the interview. As you read documents in english OR portuguese doesn't require any translation. However there is a tip thinking ahead: Birth certificate must be translated into english for the Adjustment of Status NOT K1 Interview.
2. Yes, reports can be gathered online and that's how I did. I mention that in Brazil some States do not have an online option and the applicant should get it from the police site or whatever. I assume your fiancé can get it online and if so it's perfect, no problem at all. Usually the Federal Report expires in 90 days and State Report in 6 or 4 months. I got all my reports a week before the interview or closer. To be safe just get a little bit before because we never know if we will have system glitches or stuffs like that. Once you get them online you don't need to do anything about it, they have verification codes and they can check it's legitimacy.
3. After NOA2 (I would say 15 days to be safe) you can call NVC and get your case number which will start with RDJ. To provide you the case number they will ask your USCIS receipt number, your and beneficiary dob. You don't need the RDJ number to fill out the DS 160. While filling the DS you will be asked the case number and you can add your USCIS receipt number, there is no problem at all with it and people are used to do so. In Brazil we DO NOT schedule the interview, they will assign you a date and send you the date and further instructions (Portuguese and English) for you and the beneficiary, so you can fill the DS-160 whenever you want BEFORE your interview of course. Later on the beneficiary SHOULD receive an interview letter at her residency (I say SHOULD because sometimes they never get this letter due to delivery issues and etc, however it's NOT a problem). My letter got at my house something like 2 weeks and a half after they contacted me via e-mail. The letter itself has nothing different from the e-mail they sent you, except the fact they add the visa type or something like that (We know it's K1 but they call K1-BRL). DS-260 is not an online form, it's a paper form that you fill PART 1 and take with you to the interview, nothing else. Some people say you need to sign the form there but you can sign before (I completely forget to sign mine and they didn't ask me too so I gave them a no signed form and everything went fine).
4. In Brazil we don't pay anything related to K1 online, the fee (260USD if I am not mistaken - They will let you know). Everything will be collected there before your interview. It's one fee.
5. Medical: I don't know where the beneficiary will have his medical done (RJ, MG, SP or Brasília), however it's not recommended to schedule your medical appointment until you know your interview date because they will ask you when it's going to be and additionally they basically control everything according to your interview date (When is the best moment to send the records to the Embassy..The Embassy puts all the records together as well according to interview dates). Once you know when your interview will be you can call the doctor officer and you will receive instructions by email (At least here in Rio). Everything is simple and straight forward: You will know what shots you need and exams as well (VDRL and Lung X-Ray for K1) and they need to be taken BEFORE the interview but everything can be done in the same day. Generally people who travel for their medical appointment have the x-ray and VDRL done at the same day of their interview. Usually people take care of their shots before and for free (dT, Influenza, Varicella* and MMR) - Varicella* is not for free for adults, however if had chicken pox before you don't need the shot (I don't know if other doctors request proofs but not in Rio). If you have all your previous records proving you took MMR, dT and Varicella you don't need to worry about it, however I guess that dT needs to be reinforced (Not sure, please check with the doctor). Influenza is the current year one. I know that in Brazil they just started the 2015 shots. When I had my appointment they didn't have the 2015 influenza and he just checked it was not the season for that shot and everything was fine. Exams and shots are not handled at the doctor officer (At least in RIO). The instructions will describe where you need to have your exams (Again, talking about RIO) and shots you can take wherever you want, you just need the records. The truth behind it is that the vaccination is NOT a K-1 requirement but required for the AOS. If you don't have any shot you will get your K1 (Of course if approved), however he will give you the paper as INCOMPLETE and you will need to take care of it in the States before the AOS (I recommend taking it in Brazil since it's free* - Except varicella). I like to highlight that the varicella shots are generally taken in 2 doses and depending where it's taken the second dose (Reinforcement) is taken 3 months after the first one (I went to Prophylaxis Lab and second dose was taken 1 month after the first one - 150 BRL each dose).
6. Interview you need 2 passport style pictures (Oh Gosh, 2 or 3? I forgot but you can check the instructions online as well) and medical appointment we don't need passport style pictures but 3x4 (Smaller) and I don't remember exactly how many but I guess we need 6. Generally when we take 3x4 pictures it comes on a 8 pictures combo so you will be fine!
