I would replace the charging flex first. Unscrew all charging flex area screws, lift up and take out the speaker (black-on the bottom right side), then carefully peel off the whole flex. Stick the new flex into the place and retest.
Next time use 99% isopropanol if possible. Try to open the phone carefully, check for visual damage of the button, then repair it or replace it. Keep in mind that by replacing it you will lose the TouchId function, but you will have a functional Home button.