Your opinion has little to do with it - your stand should not have any problems.
Here's a point of reference for you - if those 2x4's are Pine, they will support at least 1000psi dry - the actual number is probably higher. A 2x4 has roughly 5 square inches on an end, and you have six legs.
So assuming the lumber is free of knots and serious defects, and you have a solid top-down design (which I'm pretty sure you do, unless you put feet on it), then in theory those legs should be able to support upwards of... uhm... 30,000 lbs. (I'm also only factoring in the six legs that are pinched between the top and bottom frames)
Mind you, this is based on compression strength charts, a pile of assumed numbers, good lumber, and a random stab at what type of wood you purchased. But I think the point is clear that a hundred gallons isn't going to be a problem on your stand. Like I said earlier - a car or two.