Answer to "Bottom of touchscreen not responding?"I Suggest you to tear off the LCM and then check the touch screen-flex connector and reassemble it . The best way is to send it to apple .
Answer to "How do I replace cracked front glass"just loosen two screw on the bottom and then tear down you LCM with a sucker ,replace LCM !done
Answer to "Will this mean glass cannot be replaced?"It could be a big challenge for apple ID engineer