No, the spring brackets will not act like lower arms. They are attached to a spring, not a solid mounting point. The axle will roll when the sping flexes and you will have disastrous consequences. You need a minimum of two mounting points on the axle to keep it stable. The bracket setup you have there is unfortunately not going to work. You could use a two link truck-arm style setup with two lower mounting points, making them as long as possible to control axle movement. That would get you away from the issues you are currently having.
Also, you will need to put the center section in the axle and check the clearance between it and the spring. Looks like it's going to be awfully close.
BTW, do an introduction...
