I just broke my fingerprint sensor cable as well. Afterwards, all was normal except that fingerprint is no longer a security/login option. No effect on display whatsoever. I'd say that the display problem is a result of misalignment of the display connector (the one with the short retainer bracket). Hopefully you reconnected that again very carefully, and all was well!

I can't stress enough (no pun intended!) the need for NOT stressing these cables and connectors more than absolutely necessary! Having successfully completed the entire battery replacement and then reconnecting the fingerprint sensor connector, that cable suddenly snapped in half, probably fatiguing from too much flexing. The phone still works of course, but without a fingerprint sensor. In my opinion, this was the most crucial part of the disassembly/reassembly.

Definitely, this opening/insert is the hardest part of the procedure. I was unable to open even a slight separation with a suction cup and even with tons of heat from a hair dryer. What worked really well, and what I would highly recommend to others who experience really strong adhesive, is to use a small X-acto knife with a #16 blade. Make sure it’s a #16 (find on Amazon) because it differs greatly in angle and rigidity from the usual #11 blade. The sharpness of the blade makes it really easy to find the crack and open a gap, where you can then insert a pick with no problem.

When seating the USB-C port, use the point of a spudger to push the top corners of the port solidly in toward the cutout, before pressing the assembly adhesive down onto the frame.

These were great instructions, but have to admit this was quite a hair-raising process because of the amount of heat that was required to soften the adhesive and the amount of force needed to pry things apart. Luckily, I have a digital hot air source (Sparkfun 303D) used for surface mount electronics. The safe temperature ended up being about 200 F. If I did it again would be much easier because I know the glass piece at the top is not as fragile as I thought. So, heat gun, definitely. iOpener would be next to useless, especially to loosen under battery. But be careful not to concentrate the heat and melt plastic or make glass crack. Adhesive under battery definitely reusable, easy to peel off old battery. Go slow with the whole process and it will be successful!