How to detect resonance with DFT
The question is, if we are given a range of resonant frequencies (the &quot;dangerous&quot; range around the resonant frequency), can we decide whether &quot;the window would break&quot;, so to speak, based on the DFT alone, without a physics model (and therefore regardless of the problem, i.e. a window, a vibrating wire, etc.)?

No. There is a whole lot of physics between the spectrum of a sound track and what actual force is excerted on a window. Speaker, amplifier, wave propagation in a room, pressure distribution across the pane (both directioin and magnitude), etc.
The whole example is kind of silly. The energy required to break a window is many orders of magnitude larger than what a residential sound system can produce. Your ear drums will break long before the window shows any type of distress, resonance or not.

That is, if the amplitudes are equal, are the effects on the window's vibrations also equal?

Sometimes yes, sometimes no. In order for this to hold we have to require that

All other things are being equal
The physical systems between signal and effect is reasonably linear.