Equipment Bracket - 3D Design & Print

I have a bracket that is part of a piece of equipment that I'm building and I need to have it designed in 3D CAD program and have the part printed for the prototype. The design will eventually be used for production but need someone who understands the properties and specifications of various polymers so I can determine if a cast polymer can meet the structural requirements or if metal would be necessary as well as help to estimate costs of production for the piece. I have a basic design done in TinkerCAD and the component is approximately 4"x6"x1.5". It's a locking brace similar to a keyhole bracket used on pallet racks and will need to support the end of a 36"x1.5"x1.5" square metal tube and withstand 200 lbs of weight/torque (estimated but may not be necessary) on the end of that metal tubing. I have other parts that need to be designed as well, but this will be the most important component and, the 3D printed component could still be used to test the model even if it won't meet the engineering requirements. File of 3D part mockup to be attached soon.