I've been an electrician for many years, and in my
experience the 1/2" set screw connectors would be plenty strong.
The conduit itself, maybe not.
Anything that is strong
enough to bend it a little could spell doom.
The strait sides are the most vulnerable bit.
Since your arches will be 3" high, maybe use 5' tee posts for your uprights.
Drive them a foot into the ground.
The emt arches can be affixed to the tee posts with hose clamps.