A harmonic balancer dissapates torsional forces in the rotating mass of the engine=crankshaft..... there is a better description on wikipedia so check it out....to make a long story short it is attached to the front of the crankshaft and is attached to the big pulley that all the accessory drive belts are driven off of. (it is behind the big pulley and is the interface between the pulley and crankshaft))

There are many threads on this subject (harmonic balancer) and they have been known to fail, causing catastrophic damage to your engine. I have had it happen to mine and was able to repair it for now (knock on wood). I ended up fixing it three times now. It started with a slight noise that I could best describe by a ticking at the front of the engine under idle. I unfortunately continued driving the car for the rest of that day and it only made it 30 kms before it failed....spinning on the crankshaft nose. It is not a pleasant experience at all. I was lucky that the last fix took to the repair cause if it did'nt I was looking for a new engine. I actually have found myself a new crank (shortblock) for when the inevitable day comes that my repair job fails....I am expecting it. Do yourself a favour and find the noise before you drive the car.

I am not saying this is the cause of your noise cause I cannot hear it and it could be something entirely different. I only posted cause it could be and it would be a shame for you to go down the same road.

With the engine off... grab the balancer and try to move it in and out. there should be no play at all. check your belts too.

I think that your pic of the timing chain tensioner contacting the tab on the guide rail is normal but someone will chime in and confirm this. I don't think it is all that important that it lines up perfectly from what I remember reading but am just not positive. One of the more senior mechanics will be here to help you. I am not a mechanic.