Medical is NOT part of the NVC process. The medical only happens after the consulate has the case and they have notified the beneficiary of the consulate process for medical and interview
Best information is from the link below. Yes i have done IR5. The documents needed will vary slightly depending on the beneficiaries specific circumstances
https://travel.state.gov/content/travel/en/us-visas/immigrate/the-immigrant-visa-process/step-1-submit-a-petition/step-2-begin-nvc-processing.html
You should be using the official I. 130 information pdf for the best information on filling out the form and ensuring you have all required and recommended documentation
https://www.uscis.gov/sites/default/files/document/forms/i-130instr.pdf
Obsolete term which originated when everything was done via snail mail and instructions for the next steps were mailed in a packet to you from the consulate
Better way to think about the process is by Step 1.. Step 2.. etc .. and instructions and notifications come electronically now email or your USCIS account.
For a visit ? Definitely not if he doesn't already have a visitors visa.. and a strong possibility of denied entry, given the already declared immigration intent, if he does have one already.
Most of your questions are fully answered in the Instructions for the I130 which is found on the USCIS website
photos can be scanned and placed 4-6 to a page on a word document