I have used EMT for many years. No problems with rust arround salt waters - but more malleable than other, more conventional choices.
I bend it around a jig -laid out and temporarily fastened to the shop floor.
A simple Pine strut holds the bow up when needed.
I do not use conventional hardware. The malleability allows easy bending - in a vise. The ends get painted with a couple of coated of Rustoleum Self-etching Primer.
Any inadvertent in-use bends can usually be corrected by hand.
I have also used the "real stuff" (aluminum alloy from SailRite) - but bending is more challenging without pro bending jigs. - and factory hardware is required.
The simplest remedy to add strength to an EMT blind frame is to upsize the diameter. One inch diameter EMT can be bent in a hand bender and is many more times stronger than 1/2 inch EMT. Short spans can be accomplished with 1/2 or 3/4 EMT. Spans running the length of a boat are better served with one inch EMT.
You will not find any "load ratings" for EMT because EMT is not considered to be "structural". https://makerpipe.com/ is a source for "build fittings" to use with most sizes of EMT conduit.