How to export a large WhatsApp chat with media exactly as it appears on my phone?

So, I managed to figure it out myself. Note that this answer has been written for non-rooted devices.

1. Go to Internal Storage/WhatsApp and rename the Databases directory to Databases.old


2. Open WhatsApp, go to Settings > Chats > Chat backup and set Back up to Google Drive as Never.


3. Tap the BACK UP button and wait for the backup process to complete.


4. Go to Internal Storage/WhatsApp and zip the Databases and Backups directories.


5. Arrange a spare device. Personally, I set up an AVD with Android Marshmallow x86 and increased the storage (partition size) to 8GB.


6. Root your spare device. If you're using an AVD, use this guide.


7. Create a new folder named WhatsApp on your spare device.


8. Copy the zip file to your spare device and extract it inside the WhatsApp directory such that the Internal Storage/WhatsApp/Backups and Internal Storage/WhatsApp/Databases directories exist. We won't be needing your non-rooted device in the coming steps.


9. Install WhatsApp on your spare device, log in using your original phone number, and restore the backup when prompted to do so.


10. On your rooted device, open WhatsApp and go to Settings > Chats > Chat backup.


11. Tap the BACK UP button.


12. Install any root browser and copy the file /data/data/com.whatsapp/files/key to the Internal Storage. This is your WhatsApp decryption key.


13. Install this app, go to Settings inside the app and set the Whats key file to the WhatsApp decryption key you just copied.


14. Go back to the previous screen, select the File type to your preferred file type and hit Export to storage.


15. You'll find the exported chat files in Internal Storage/BackupTextForWhatsApp.

To reactivate WhatsApp on your original, non-rooted device, just open
WhatsApp on your original device and verify your number again. Your chats will still be there.