I am arriving in Beijing Capital Airport T3 at 6:35 on 21 April from Kuala Lumpur

Unfortunately, if all flights are on time, you might not make that connection. It would literally take you 60 minutes (yes, even that early in the morning) to pass through the transit security check. They are notoriously slow (i.e., very thorough in re-checking your carry-ons). I would suggest you speak with an airline rep to see if you can have them expedite you to the front of the line seeing how you have a "short-connection". Good luck.