The Lone Wanderer’s destiny resides in the Project Purity chamber. Official canon is that he/she didn’t die at the “end” of the game.
The damage bonus is useful, especially since its unlikely any companion will provide +25% damage output.
Lone wanderer is nice, but you’ll get better weight reduction with strong back,and armor/damage resistance is a non-issue after ballistic weave. Then press the corresponding button to equip him with a piece of armor (Triangle on PS4, Y on Xbox One, and T on PC) just like you would do on any other companion. Simply call Dogmeat over, initiate a trade and give him the dog-friendly items. There are collars, bandanas, and dog armor hidden throughout the world.
