In om PC but I prefer playing with a gamepad.
General info
My General sensitivity was 8.5, but I recently toned down to 7.5.
Blunderbuss aim is either 6
Pistol aim is 4.5
EoR aim is 4.5
I have my jump button mapped to my Right Bumper
My food to A.
My objectives/voyages to D-pad right.
When it comes to Sensitivity, I think its OK to have low sensitivity, but try to go tiny bit higher every time you have become comfortable with your sensitivity. Higher sensitivity does not necessarily mean better, but being fast enough to snap around can be nice. If your snapping around is inconsistently off, you may be too high in sensitivity.
My first things that got me to play better is to relax and think more about being in a stance that you are certain of, than being in a stance that gets you to Panic. So for example in arena: I can continue to stealthily be stealing the enemies chests and hand them in, and there is only one more. But there is one person inside that is about to come up and maybe spot me. Do I get rid of him while he doesnt see me? Or risk stealing the treasure? After stealing 4 chests, I made the choice to go after him in the claustrophobic spaces of the galleon, I managed to loose track of him in such a way that even M&K would and got killed in the sword fight. I put myself in a place I am just not comfortable with.
Another example is: Thinking about ship tactics more than Boarding has made me more succesfull. So My loadout has become mostly Pistol+Blunderbuss. With ship tactics only, I try to not get borded, so my blunderbuss is my main gun in thwarting boarders from the ladders and fight them if they ever get on my ship. But pistol for assisting teammates, indoor fighting (funnily enough) or underwater fights.
Look before you aim is a another thing that helped me in pirate fights, and that comes mostly with patience, and accepting to not desperately kill anyone when I think im about to kill them before they heal up, as that puts me in a bad position. So with Guns, I look without aiming and evaluate when to start aiming. When I do aim, I try to make my shot within 0.5 or maybe 1 second of aiming. If its longer, im becoming desperate.
Maybe we are the same, but I have an easier time hitting someone with my pistol after a reload, and that is usually because im out of aim, reloading and walking in a defensive manner. The timing of when the reloading is complete puts me in a good comfortable aim outside of aiming, enough to aim down and shoot straight after. Sorry if you dont understand, but its just a subtle game flow that I noticed in myself, and im just applying outside of reloading.