Failing: sleep, rotation, headphone, mic, cams and some weird stuff

I have bought this cheap iPad 4 use as a home automation center, mounted on the wall. The description stated it had a few defects, which I thought I could get over. Upon closer inspection some more things are wrong with it:

• Touch screen was flakey (ribbon cable was sheared)
• Sleep by pressing the power button is not working, not even from assistive touch. Hold to power down ís working
• Screen rotation: not working, does work from assistive touch. Screen lock switch is working, so are the volume buttons
• Headphone jack: only some loud pops and light noise
• Microphone: no input (Siri cannot hear me)
• Cameras: both front and back camera show only black
• Apps from the app store cannot be installed: after pressing “Install”, spinner keeps on spinning without any popup
• Apps cannot be deleted: long press does bring up wobbly icons and the ‘X’, but pressing the X does nothing
• After the first boot, the screen stays black. You can tell it is on because when initiating Siri (home long-press) or taking a screenshot, you can hear the corresponding sounds. After a reset (home + power long press), you can get to the home screen by pressing the home button (the home screen does not show itself automatically)

I already replace the touch screen (working OK now), home button and WiFi cable. I can see no damage to the logic board, and judging by the screws, it has not been removed.

I was thinking about replacing the headphone jack assembly, since this connects all the components which are (partly) failing: iPad 3/4 Wi-Fi Headphone Jack

The hardware issues seem logically connected to this part, but I have no clue about the seemingly software-related issues.

Any ideas that replacing this part will fix my hardware and/or software issues? Thanks for any input.

Edit: FIXED

Everything is fixed after I replaced the headphone jack assembly! As you can see below, this part was torn by the previous owner. Thanks for the hints.