Yes, I guess that "the chance that a tornado sweeping through a junkyard might assemble a Boeing 747 » is not null. But we would rather not consider this type hypothesis if we are to remain in the domain of science!
There are only 3 causes that can explain an object, i.e., chance, necessity or design. If you can rule out chance or necessity or a combination of both, then design is the explanation and you don’t need to compute the probability of design to draw a design inference. According to ID theory, objects exhibiting high level of FI can’t be produced by chance or by necessity or a combination of both. Therefore, they are designed. This is ID in a nutshell.
As far as biological objects are concerned, I think this is indeed the only real issue here. ID theorists think that as a rule of thumb, most fonctional protein are very rare in the sequence space. If true, ID wins. If wrong, ID may be in trouble. My take is that most functional proteins are very rare in the sequence space. But I will let @gpuccio elaborate on this point if he want.
You are committing here the Texas sharpshooter fallacy.