One thing you definitely do not need to worry about is frame strength and material. Pound for pound, aluminum is stronger than steel, and many many people at or above your weight are happily riding aluminum bikes, especially the Trek FX series, which has a great number of 'Clydesdale' class fans.
As mentioned above, the problem with the bke were not only your weight, but the inability of the shop to perform the maintenance that would have prevented the failures, esp., properly installing cranks and properly tensioning and stress relieving spokes (almost always a problem on machine built wheels, unless an experieiced wheel builder 'tunes them up' before you take delivery).
Perhaps if you weighed 150 lbs you wouldn't have discovered these problems, but more likely it just would have taken a bit longer.
Go to the 'Clydesdale' subforum and see what they are talking about today. Us big guys have problems that a lot of 'normal' sized riders don't have to deal with.