You can't have & in your apple id, in fact I know of know other service that would allow to create an email address that way.
You use your apple id for facetime, you can have muliple email addresses associated with your apple id. One device can use one address, the other device can use another. Technically, both are using the same apple id, but are using different email addresses to sign in with.
Go to your apple id management site to change/add/verify
My Apple ID
Using FaceTime http://support.apple.com/kb/ht4319
Troubleshooting FaceTime http://support.apple.com/kb/TS3367
The Complete Guide to FaceTime + iMessage: Setup, Use, and Troubleshooting
Troubleshooting FaceTime and iMessage activation
Using FaceTime and iMessage behind a firewall
iOS: About Messages
Set up iMessage
Setting Up Multiple iOS Devices for iMessage and Facetime
FaceTime and iMessage not accepting Apple ID password
Unable to use FaceTime and iMessage with my apple ID
For non-Apple devices, check out the TextFree app https://itunes.apple.com/us/app/text-free-textfree-sms-real/id399355755?mt=8
How to Send SMS from iPad