You really need to research the Grid Rules indepth. The old link I had appears to be dead. The short explanation is at ages 50 and 55 the criteria lessens to be found eligible for SSDI. If you would be found eligible at 55, than it means you need to show better documentation to strengthen your case now. You're close to proving your case in other words.

Here's a decent link. : http://www.ultimatedisabilityguide.com/grid_rules.html