Should I delay graduation a semester and transfer from IU to a target?

Delaying graduation one semester is not a big deal at all if it helps you achieve your goals. The thing I would seriously consider is if going to another school would really change how your network perceives you (unless you get into an Ivy or big target). If you have a solid resume and are prepared, it really shouldn't matter if your school's alumni are douchebags. You only really need one mentor that's willing to give some advice and the rest can be done by just grinding.

I've had experiences trying to contact alumni to help me get an interview and they just never responded. Eventually, I decided to take matters into my own hands and reached out to others at the bank. Ended up getting a superday and then an offer without the help of the alum that was there (although he did take me out to dinner the night before the superday after finding out I made it to final rounds). Networking is everything, but remember that you can choose your network if you're willing to work hard enough.