Glitchy phone screen after re-repair after taking to mall shop

Hi everyone, about 4 months ago my screen was damaged (cracked), and so I took it to one of those mall shops that does phone repairs since I needed a new screen ASAP and couldnt wait for a part to come in. However, after they repaired it, it promptly got water damaged again, and when I opened it up with an iFixit screen on standby, the water resistant sealant was completely missing and the whole phone smelled like burning.

Furthermore, the battery on the phone dies when it reaches about 10%, and I suspect they may have swapped my back casing and taken the old battery or some parts with it. I replaced the screen with an iFixit part, which worked for the most part -- except the screen randomly selects other letters when typing as though someone is pressing on random parts of the screen. It was inconveniencing but not enough to warrant an immediate response from me as I wanted to see how it would evolve over time, and if it was worth getting another screen (I didn't expect to be able to get a free replacement screen or refund without sufficient evidence).

Now, however, the problem has gotten worse -- the screen randomly presses buttons constantly, and some keys on my keyboard are inaccessible (when pressing 3, my screen will input a 2 and 4 simultaneously, for instance). Worse, at random times the phone will begin intensely glitching, the screen will start shaking vertically as though someone is repeatedly trying to swipe it down/up at high speeds, and it will open random apps and press random buttons constantly until it resolves, almost like the phone is having a seizure.

What should I do? The warranty is void for several reasons I'm sure, I can't trust the mall shops that have sold me defective parts numerous times, and I'm worried that the screen itself might not be the problem and that the interior of the phone may be damaged beyond what I can recognize (however, to my knowledge I performed the repair perfectly, with the exception of the microphone assembly which came completely off with a miniscule amount of pressure).