Based on UL2239's specification for straps and hangars, a 3/4" EMT strap needs to support a minimum of 100 lbs. However, manufacturers are required to guarantee 3x safety load ratings for the straps/hangars.
There are toggle bolts that will easily support 100lbs, but that is entirely reliant on the strength of the wallboard. The wallboard is the primary issue, not so much the fastener.
If this were my installation, I would find the joists and use 2" screws to attach the straps. In instances where the EMT runs parallel with the joists in places, I would use pieces of unistrut or 5/8' x 1.5" wood to bridge the joists throughout the run. It may not look pretty, but at least you are not relying on paper and gypsum to hold up your raceway.