You've been hit with the "brittle brown" syndrome. For a stretch of a few years, about a decade ago, the reddish brown color (and dark red) was defective and known to crumble and break. Lego has since changed the formula for those colors and newer pieces are unaffected.
Yes, Tamiya cement will work on Lego but the plastic along the seam will melt if too much glue or if too much pressure is applied. The seam will be visible even if expertly glued but in most cases the piece will be completely functional.
In your case, I believe the piece is likely to be part of that bad batch and it'll just break again after repairing.