Blaming your tools only gets you so far...
If you want to stick to regular layouts then consider something like Bumper Jumper. The idea is to have most of the important actions on the shoulder buttons (the bumpers and triggers). That way your thumbs spend more time on the sticks... you know, doing important things like aiming (or looking for an escape route).
Personally I have jump and shoot on the triggers, and grenade and melee on the bumpers.
And don't forget to invert your Y-axis! Only crazy people have it the other way round.
Just ramp it straight up to 4 or 5 (max) and leave it there.
The only time you would reduce your acceleration is if you had insanely high sensitivity - which is generally not recommended.
Start at 2 or 3 and slowly work your way up to a max of around 5 to 6. Infinite has a lot less aim assist than Halo 5 - so you will probably struggle with the faster reticule movements.
Don't be afraid to drop back a notch if you are struggling or haven't played in a while.
A lot of the pro-players actually use fairly low Sensitivities. Even as low as 3. They then concentrate on moving the reticule early to where they think the enemy will appear.
You can also set separate horizontal and vertical sensitivities... and if you do the general recommendation is to have your horizontal slightly higher.
Each stick has four zones.
The terminology can be a bit confusing, but essentially, from inside out we have;
The centre dead zones are simply an area where your sticks won't register any movement. You set it as low as you can before you start getting any stick drift (movement when you aren't touching the stick).
The next zone is the Axial Dead Zone. This is an area where your sticks won't register any diagonal movement. It's a preference thing - but most of the time you just need a little tweak in a horizontal or vertical axis. And this can make small movements of the sticks feel less "twitchy".
The Normal Movement Zone is the biggest region. It's the rest of the stick area - and you are free to move in all directions at your specified acceleration and sensitivity.
And the final, outer zone, is the Maximum Input Threshold. This is the point at which your stick registers at maximum movement. If you set it at zero then you have to "peg" the stick (hit the edge) to get maximum movement. A higher setting acts as on outer dead zone and lets you hit full tilt before you peg out.
Set the central dead zone as low as you can to prevent stick drift.
Set axial dead zone to 0 (probably doesn't make a lot of difference).
The important setting is the Max Input Threshold (how quickly it registers max input). Setting this to 15 will make the stick as responsive as possible, and give you a crisp strafe. But be careful, a faster strafe makes you harder to hit, but it also makes it harder for you to aim and shoot back.
Set the central dead zone as low as you can go to prevent stick drift.
Set the axial dead zone to 12.
And for this stick you want more flexibility and fine control in aiming. It's the opposite of what you want with the move stick. So set the Max Input Threshold as low as you can. Start at zero. This will give you a larger normal movement zone.
A low FOV makes it a bit easier to aim as your enemies will appear closer to you (a bigger target). But this is also offset a bit by the fact that their strafing back and forth will appear faster.
A wider FOV gives more spatial information (you literally see more) and a better sense of speed. But things look further away. And the smaller targets are generally harder to hit.
Personally I like it sitting about 90 to 95 degrees.
Press the Big X to bring up the side menu.
From there it's normal 'X' to record a clip. And 'Y' to take a screenshot.