Why isn't my blow function working for my stun sword?

My function (based off the generic link sword blow function) is part of a stun sword. I have two problems with it that I'm stumped on.

function blow(hit)
    if (hit.Parent == nil) then return end -- happens when bullet hits sword
    local humanoid = hit.Parent:FindFirstChild("Humanoid")
    local torso = hit.Parent:FindFirstChild("Torso")
    local vCharacter = script.Parent.Parent
    local hum = vCharacter:findFirstChild("Humanoid") -- non-nil if tool held by a character
    if humanoid ~= nil and hum ~= nil and HitDamageEnabled == true then
        -- final check, make sure sword is in-hand
    humanoid:TakeDamage(20)
    local hitani = Instance.new("Animation")
    hitani.AnimationId = "http://www.roblox.com/Asset?ID=1588878466"
    hitani.Parent = humanoid.Parent

    local hitTrack = humanoid:LoadAnimation(hitani)
    hitTrack:Play()
    humanoid.Walkspeed = 0
    torso.Anchored = true
    --HitDamageEnabled = false
    wait(1)
    torso.Anchored = false
    humanoid.Walkspeed = 16
    --HitDamageEnabled = true

    end
end

1. When I hit an enemy, it kills them in one hit, instead of dealing only 20 damage.

2. The anchored and walk speed aren't working. The player can still move, not sure what to do about this. Thanks