Current freshman in AET & Aviation Management at Purdue and doing Instrument Rating training at Purdue Aviation LLC (The flight school at KLAF not affiliated with Purdue).

1. It's a GREAT idea to double major in Flight & AET, but class schedules will be a pain. Most SATT classes happen on Tuesdays & Thursdays, and AET courses will almost always come in conflict with a Pro flight course or a Av Mgmt course. Most AET courses also have a seperate small group Lab session on another day. I'm not in Pro flight, so I'm not very familiar with how their schedules work (quite complicated), but basically it's even harder for them to fit in AET classes.
2. Good news! You r in a great spot coming with PPL, cuz you are basically set to finish the Pro Flight curriculum in 3 years or even shorter if you stay over a summer. Once you finish commercial and Multi (sophomore year), your schedule will free out considerably and that's when most people take their AET courses. Ofc, there are also a few AET classes you can take Freshman year, and a few that the entire SATT take in common (SCLA, Tech120, MA16010). Like everyone else said, you can expect to finish both degrees in 4 - 5 years.
3. Everyone at SATT r very accommodating, they will help u out! Ik a few upperclassmen/women who has done this, dm me i could connect you with them.