iPhone SE boot loop after already repaired water damage

Alright, as you might suggest by the title, this is a problem that came up about a month after the first 'accident', so let me get you up to date:

-fell into river with my Iphone SE about 1 month ago (stupid, I know)

-Phone was submerged for ~30sec-1min in my pocket

-screen had lines over it and it had noise coming from the speaker and it shut itself off after a couple of seconds (power button not working anymore)

-dried it and put it in rice for 3-4 days

-not turning on, so I opened it and cleaned the motherboard and all pins with isopropyl

-left opened to dry for another 2 days and changed the WIFI antenna because I ripped a cable (stupid again, I know)

-Closed it up turned it on, working perfectly besides the power button not working and some tiny water marks on the top edges.

Alright, this is where we left 3 weeks ago until yesterday.

I was planning to change the screen and power button in one go when it would go on my nerves just too much. over time in the last 2 weeks though, the screen started to have some kind of burn-in effect where if you had an app open for some time it wouldn't wholly disappear after closing.

similar to this but more at the corners and not in the middle, like a vigniette

So I planned on changing the display as soon as i'd find time.

Ordered a new screen 2 days ago and yesterday it happened.

I plugged my phone into my computer to charge and after maybe 3-4 minutes (the screen was turned on from use) the screen suddenly turned bright red and after 3-4 seconds it shut off.

then it just entered a boot loop with the apple logo showing for a couple of seconds then a 'blue screen' (mostly white or some off white color) showing for a couple off seconds, it shutting back off and repeating the whole shabang.

it did it the whole night now so that the battery was fully drained this morning.

Now what my main questions are and where I hope to maybe get some help or input from you guys: I read an article stating that an issue with the proximity sensor flex cable could be responsible for this aswell as maybe a wrong (too long) screw for the cover of the lcd cable. I tried ruling out the prox cable one by trying to boot it up without the cable attached but nothing happened so I'm not sure I did it right.

What would you do to rule out one of these 2 possible mistakes?

Also, could it even be the screws now that it had been working just fine for over 2 weeks after me opening it....

Would you try to replace the screen (it's a full front panel so it would also have camera plus prox sensor) if it arrives (propably) tomorrow?

I'd be really happy for any input or advice from you and thanks a lot in advance already for ANY answer since I don't want to give up the phone just yet!

And have a nice day :)