Another person of interest is Lance, whose quests received a detailed walkthrough on this page of the Assassin's Creed III Remastered guide.
The Whittler's Weapon
In the designated spot you will find a burning cart and a group of bandits.
Quickly defeat the men, approach the line hanging from the rock and press the interaction button to save Whittler.
Tools of the Trade
Speak with Lance and afterwards meet with him in his old apartment in Boston which will be marked with the Homestead icon.
There you will learn that his workshop has been sold.
Start off by asking the former co-tenant of the carpenter and afterwards follow the man.
You need to stay behind quite a bit, as your friend isn't good at hiding.
As you finally reach the destination, wait for the thief to walk away and take the tools from the chest. That way you will end the mission.
Thousand Pound Idea
Lance will ask you to head to New York and collect a package for him.
Unfortunately, in the harbor it will turn out that the plans were taken by his former apprentice. To regain them, you need to kill three designated men.
Try to do it silently, so that you don't raise the guards' attention.
With one of the enemies dead, approach his corpse and search it with the interaction button.
After regaining all parts of the document, take them to Lance to end the mission.