The so-called letting Anthony come means that Ange will let go and do his own thing. After Anthony has arranged it, he will tell him what to do. It is commonly known as the hands-off president.
Quietly shrinking and shrinking, Ange slipped away "quietly". Of course, this "quietly" was in double quotes. Everyone else saw him slipping away, but they all knew his temper and were too lazy to stop him.
After slipping out, Ange decided to slip a little further and flew deep into the mist of chaos for a few minutes before stopping. (Remember the website address: www.hlnovel.com