1) How accurate does the 3.5 volts need to be?
2) An ordinary alkaline 9V battery cannot supply 1 Ampere without dropping voltage drastically and rather unpredictably. It might even be below 3.5 volts at such a high current. You need to find a heftier source.
https://www.youtube.com/watch?v=rG2ozSOvxBY&t=3s