Ghost Touch + Battery Charging Issue

I bought a Nexus 5X form the local craigslist, the phone was working fine and had no issues in a quick 5 minute check (longer wasn't possible), when I brought it home and put it on charging for the first time, using a Qualcomm QuickCharge 3.0 Charger, I noticed that the charging time that is displayed on the lock screen was vanishing for a few moments and coming back itself, the charge was not carrying consistently. So I switched the charger back to the stock one and check the readings on Ampere App. As it happens, the charge was not consistent on this charger either, it was charging fine once plugged in then going back to 50A or 100A in a few minutes then someitmes coming back to 1800A and sometimes staying that way until I plug out and plug in again after a few minutes. I cannot return the phone since the seller is not accepting that this issue existed when he had it. I then charged it with the screen off in one go and continued using it for a day and now I have ghost touches, frozen touchscreen, and issues with the radio dropping. My QuickCharge charger is absolutely fine, because I have been using it on my previous device, Lenovo ZUK Z1 for months. On the Nexus 5X, oddly, it does not state to be "Charging Rapidly" with this one, it does say on the stock charger. Hardware repairing in Pakistan is not crafty and I need to know what is causing this issue before I get the phone opened. Another thing worth mentioning here is that my headphone jack does not work properly, I get a noisy frequency like sound when I plug it in in the left ear, nothing in the right; I do not know whether this issue was here before all this touchscreen issues or not because I plugged it in today for the first time. Can someone please shed some light on this? Or tell me how to do some kind of diagnosis about voltages (that's my theory) so that I can get an idea of what to get fixed. Thank you for the help!

Update: The MIC has also started to behave improperly now, the other party cannot hear my properly, voice breaks, perhaps this is related to the radio, I am not sure.

Update 2: The battery is now charging just fine with the stock charger and the ghost touch and frozen touch is now gone itself, but the headphone jack doesn't work and the radio drops when I am about to get a call so it does not ring at all, can this be the result of an incompatible charger or current flow?