yes there is a washer behind the large 30mm nut
the torque for the nut is 150lbs/ft OR MORE but less than 250lbs/ft
you NEVER reuse that nut, always replace with new
why your bearing locked up? i dont know.....
normally the axle might not fit 100mm or 90mm...but since you didnt change anything except a bearing....
yes you can get the spindle+bearing+hub all completely assembled from http://www.partsplaceinc.com/