If the HS counselors aren’t putting current info into Naviance, then the scattergrams won’t be helpful (and their categorization function when searching schools is inaccurate as you noted, showing Purdue as a safety).
None of the college admission sites are likely to be accurate because they don’t take into account some important aspects in the admissions process (at least at holistic schools)…e.g., essays, LoRs, ECs. They also can’t categorize likelihood of admission by major. And you are right, aerospace engineering is generally going to be more selective than a given school’s overall acceptance rate.
For aerospace, depending on your stats, some safety schools could include Iowa State (stats based admission rather than holistic, formula is on their website First-year Students - Iowa State University), ASU, and U Alabama Huntsville. I agree with the poster who said that posters on CC will be able to help you create a good, balanced college list.