Route your new belt from the water pump to the alt. and then to the
corresponding  crankshaft pulley groove. I am guessing that you are putting
the belt on the groove for the a/c or powersteering.1/2 inch belt
deflection in the middle of the largest span with moderate pressure is the
tightening spec.(real scientific ). Does you van have a/c and powersteering?
If not, cant imagine what is chewing up your belts.The bracket that is on
the bottom of the alt.is much stronger than the brace you are looking
at.This bracket will aligne the alt.Is it tight? The bentley shows no
spacers. Is a alt. fan blade bent?