My parts come with adhesive on the back of the flex where the microphone is. It is worth adding that the black bumper beneath the microphone is part of the microphone assembly and should be taken off the old flex and attached to the new one. The bumper that is screwed down above the microphone should hold it securely in place against the bottom one, but obviously if your flex doesn't come with adhesive on that particular area you will need some double sided tape or something similar to hold them together

You may find it easier to leave the bracket on the speaker housing and just slip the wire out of the bracket. Then as you put things back together, attach the connector before slipping the wire back in to the bracket as you will have more slack this way for connecting it up

I agree. I found it much easier to attach it before slipping the wire back into the holder in the bracket as you have more slack to play with. Or if the wire was removed still in the bracket from the speaker housing as the guide says, it would be easier to reattach the connector before screwing the bracket back down (again, more slack)

It isn't necessary to remove the screen as long as you can support it properly while doing the rest of the work. In my experience, unnecessarily removing screens can do more harm than good and causes extra work for yourself