No need to grab if you bind the animation like these.
elseif IsButtonPressed(15, 0) then
PedSetActionNode(gPlayer, "/Global/G_Johnny/Cinematic/ThroatGrab", "Act/Anim/G_Johnny.act")
Wait(0)
PedSetActionNode(gPlayer, "/Global/Actions/Grapples/Front/Grapples/GrappleMoves/PowerBomb", "Globals/BOSS_Russell.act")