Hi and welcome to the forum
I have n FP3 and get between 1 and 2% over 16hours when in aeroplane mode.
Do you have any data you cannot retrieve as you could do a factory reset or maybe as you only installed 1 app and removed it you could try starting in safe mode.
Finding the culprit piecemeal can take some time.
Aeroplane mode should disable WiFi, Network, Bluetooth and NFC
I’m sure I have a few apps that try to connect during the ‘night’ but as they fail they use limited power, etc.