I looked again to see if I was imagining things. The first picture I see is all screws and nails? The bits above as well as behind the chair are the parts that concern me. Lots of pieces that can shear off and drop that arm in your lap. One of those cleats has a screw going in at a very acute angle. for instance.

I'm going to quibble with the other response about the arm above being over-engineering. You're copying existing designs instead of trying to work out your own geometries. You could probably move the moving parts behind the monitor, but I don't know how hard a time you'd have keeping the footprint from increasing.