Your WTF picture is of magazine loaders for use with stripper clips. I did get a kick out of that!
I think your barrel length is okay (minimum 16" to be legal) Put a cleaning rod down the barrel with the bolt closed and mark where the end of the muzzle is on the cleaning rod. Pull it out and measure it. I think you'll find it just 16".
I think it is a nice looking sporterized carbine. There is not much in the way of collector value as a whole carbine but it looks good. I would put the value on it in the $300.00 range. It is worth more parted out.