Not sure if I did it right but there are still a few emojis showing up as white.
In your linked file there was a 'META-INF' folder and a 'system' folder, I took the tff file from the system/fonts folder and applied the steps in the OP.
Were there additional steps or did I do them properly?
Using Hangouts the "missing" emojis were fixed here. Whatsapp was always fine. Don't use other apps myself where emojis are an issue...