loosening bolt on the steel support strut that's secured to the ceiling of the garage
It looks to me like a bit of a can of worms.  

The perforated angle iron is set up so that the holes are right on the edge of the vertical drywall - there's nothing solid for them to anchor to.  But you don't have much flexibility placing the track, it has to line up with the door.  That jog in the ceiling is in a very inopportune spot.  

It's a bit of a hack, but you could drive screws at an angle and maybe, hopefully, hit wood framing behind the drywall, and get off easy.  

Otherwise you'll have to remove the drywall and extend the structure out so there's something above the angle iron to attach to.  

If you're lucky it may be an I beam behind there, and beam clamps on the flange may work out.  

If it's a glue-lam beam or something you could just nail a 2x4 to the beam to use as a cleat for the screws.