After one month of Mutiny the crew will approach you and say that you need to divide. I only had one boat, so they could not take a boat, and I did not sail into and out of ports to see when the men would start quitting, and what percentage of the crew would quit. I only tested up until the Mutinous stage. Maybe, I'll do some testing on the total effects of Mutiny at another time.
Those tests were done with no items and no specialists. Adding a Cook delays the start of the decline in happiness by one month. Adding a Concertina also delayed it by one month. I was unable to add just a violin, so I am not sure what effect it may have. When I added the Concertina, I had both items. Adding both the Cook and Concertina delayed it by two months. Adding a Quartermaster had no effect on the first 3 happiness levels, but delayed the onset of Mutiny by one month.
I tried it at 50 gold per man, and at 0 gold, and those numbers dropped. I wasn't going to spend several more hours sailing around with different amounts of gold to find out the results. Just know that you will not get those numbers if you have less than 100 gold per man.
And, as I was sailing around killing time and watching the months go by, I watched my food level drop, So I did some testing on that while I was testing the other. I was in a Treasure Galleon so I could hold the max amount of food. When I started the game it said 132 tons of food was 26 months worth for my crew of 100. That 26 months worth ran out after 12 months. I then added a Cooper and the same 132 tons of food was now good for 40 months, and exactly 1 month of food was used each month. So, a Cooper does his job for sure.