By Jim Harrington [email protected] Van Morrison seemed intent on proving a point. It began when he first took the stage on Monday night at the Fox Theater, promptly — as is his wont — at the scheduled set time of 8 p.m. His first notes of the evening weren’t sung, but rather blown thrown an alto saxophone. He followed that brief instrumental with a vibrant take on “Close Enough for Jazz,” from his 22nd studio album, 1993’s “Too Long in...