I have this exact issue. I have torn things apart for years, so I have a good feel for when things go right, and I took my time taking the phone apart,but it won't boot. No recovery, nothing.
My old screen is smashed, and I need this fixed. I am assuming you just bought a new phone instead.
If you made any headway please let me know, I am fixing my son's phone, and he has been devastated since dropping his phone.
Any help is greatly appreciated