Nimble Escape. The goblin can take the Disengage or Hide action as a bonus action on each of its turns.

Just What we Needed. Bob can take whatever actions the party collectively decide to tell him to take, he will also preform the action if the party doesn't sees him but already told him to preform (he is free to use it's bonus action as long as it doesn't directly conflicts with it's current orders). 

I Will Leave the party. Bob cant be targted by an Area of effect attacks that will kill him and if he is cuaght in one he cant take damage from it unless it will not kill him, but he cant use the not on the party's watch ability for [roll]1d4+1[/roll] turns, and he cant use this ability until the next [roll]2d20dh1+2[/roll] short rest.

Scimitar. Melee Weapon Attack: +18 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 18) slashing damage.

Shortbow. Ranged Weapon Attack: +18 to hit, range 80/320 ft., one target. Hit: 5 (1d6 + 18) piercing damage.

Not On The Party's Watch. the closest party members take the next 100hp Bob take from attacks and all attacks have disadvantage (can stuck with other disadvantages) for [roll]1d4[/roll] rounds (the number of rounds applies to both the hp party members take and to the disadvantage) .

Attacks Of Opportunitie. Bob makes [roll]1d6-2[/roll] attacks against the closest creatures.