You should definitely offer him a happy birthday but no gift or card. Keep it short and sweet. Don't ask him about his plans, etc. It will be very tough, but keep with the detaching route.
In terms of the three week thing...just do what you were doing before in terms of just staying busy and if he calls to talk, keep the conversations strictly business and when it starts getting too friendly, say you have to go and that's it. Always be the one to cut off the conversation.
Then play it by ear. After the three weeks or longer, you can call to talk to him about something, then offer to meet him for coffee at a later date. Something small. No lunch and definitely not dinner. Then when you meet him, you show him your hottest self. After three weeks, he'll start forgetting the little things that made you attractive. You can even flirt a little and be playful but don't give in. It's the idea that the person who wants the R the least is the one with the power. So make like you've been doing great without him. Then go from there.
I hope that makes sense.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.
