You may be able to use Accessibility features to use other functions to approve transactions. You may also want to make an appointment at an Apple Store to receive some specialized help to assist with the side button and various options and settings.
Assistive Touch can be setup to transfer the double click to a different setting/action so that you can better manipulate the function.
Use AssistiveTouch on your iPhone, iPad, or iPod touch - Apple Support
It’s not difficult to learn, but in-person assistance is best, in my opinion. I’m more than happy to assist if you want to go this route.