Is that a New Dimension Zeroflex?
Your pics don't really tell where on the tower they are located. I've ridden cracked aluminium mtb frames for a season and not had a catastrophic failure. I wouldn't be comfortable with it on a tower. Unless you know a top notch tig welder that can heat treat the tubes you should be looking for a new tower. A weld job may buy you another season or two if you stop pulling barges and tubers.