man-o-man what a sight
Those fasteners in that exhaust cam sprocket should not be that hard to remove. I would try another "high quality" torx socket on them.
Your biggest headache is going to be getting that "pin" on the right hand slide rail out - especially since it is now cut at the head. It looks like a job for a machine shop now. I would proceed with removing the lower cover and maybe consider just pulling the lower pin on the right hand slide rail and pull the rail out with the cylinder head. I don't think you are going to have anything to get a grip on the upper pin with it boogered up like it is.
I would recommend replacing those wire "markers" with tie wraps that have to be cut off, that way you can be assured of not losing that orientation. I thought I remembered the chain itself being marked for proper orientation at #1 TDC but my memory leaves alot to be desired anymore.