iPod Touch Not Working Properly After Front Screen and Housing Replacement

So my son left his iPod Touch 4th Gen on my back bumper and it fell off out in our dirt/gravel driveway. I finally found it, 7 days later, run over multiple times😐. Front screen and back housing were demolished as you can see, but it still worked fine (except rear facing camera was done). Ordered the rear camera, front screen and back housing assemblies off eBay from reputable sellers. Took it all apart and reassembled it. Bada bing! Everything was working fine: camera, speakers, touch screen, wi-fi, all of it, for about 2 days 😢. It went from working perfectly, to being kinda glitchy (had to hold home and power to restart), to not turning on at all. I read somewhere that if you don't clean all metal to metal contacts, it may interfere and not work properly, so I just took it (almost) all apart again, cleaned the contacts, and it turned on and was working, but this time only for about half an hour. I've held down the home and power buttons for long periods of time, which sometimes got it to work, but now is not working at all. Any ideas on what might be going on??? Is the screen bad? Did I maybe miss a metal to metal contact (e.g. the power button, ribbon cable)? Any really important ones that you can tell me about? I really don't want to take it into the Apple store, but if I do, any ideas on a ruff guesstimate on what it's gonna cost me? Thanks for any help! I really appreciate it, I'd love to get this thing working for my 7 year old so I can have my d*** phone back!

Before

After

(my kid scratched up the back already, gotta love it)