IMO, when putting an AMC, you can:
1. Using AML-AMC-AMR if you don't have real ML / MR. Other wise, you can put down the AML, AMR for more balance formation
2. No, you should still attack down to both flanks. However, if you see it's hard to win through the flanks, try to attack into the middle
3. You can use MC or even ST for AMC instead, but remember not to use regularly.