One iTunes account, several users and several devices. How can I make it work?

Have a read here...

https://discussions.apple.com/thread/3958277?answerId=18409815022#18409815022&ac_cid=ha

And See Here...

How to Use Multiple iDevices with One Computer

Also have a look here...

http://macmost.com/setting-up-multiple-ios-devices-for-messages-and-facetime.htm l

Assign a different email address (free gmail.com?) to each device.

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

http://tinyurl.com/a7odey8

Troubleshooting FaceTime and iMessage activation

http://support.apple.com/kb/TS4268

iOS: FaceTime is 'Unable to verify email because it is in use'

http://support.apple.com/kb/TS3510

Using FaceTime and iMessage behind a firewall

http://support.apple.com/kb/HT4245

iOS: About Messages

http://support.apple.com/kb/HT3529

Set up iMessage

http://www.apple.com/ca/ios/messages/

iOS 6 and OS X Mountain Lion: Link your phone number and Apple ID for use with FaceTime and iMessage

http://support.apple.com/kb/HT5538

How to Set Up & Use iMessage on iPhone, iPad, & iPod touch with iOS

http://osxdaily.com/2011/10/18/set-up-imessage-on-iphone-ipad-ipod-touch-with-io s-5/

Troubleshooting Messages

http://support.apple.com/kb/TS2755

Troubleshooting iMessage Issues: Some Useful Tips You Should Try

http://www.igeeksblog.com/troubleshooting-imessage-issues/

Setting Up Multiple iOS Devices for iMessage and Facetime

http://macmost.com/setting-up-multiple-ios-devices-for-messages-and-facetime.htm l

FaceTime and iMessage not accepting Apple ID password

http://www.ilounge.com/index.php/articles/comments/facetime-and-imessage-not-acc epting-apple-id-password/

Unable to use FaceTime and iMessage with my apple ID

https://discussions.apple.com/thread/4649373?tstart=90

FaceTime, Game Center, Messages: Troubleshooting sign in issues

http://support.apple.com/kb/TS3970

How to Block Someone on FaceTime

http://www.ehow.com/how_10033185_block-someone-facetime.html

My Facetime Doesn't Ring

https://discussions.apple.com/thread/4155326

To send messages to 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

http://www.iskysoft.com/apple-ipad/send-sms-from-ipad.html

You can check the status of the FaceTime/iMessage servers at this link.

http://www.apple.com/support/systemstatus/

 Cheers, Tom 😉

You don't need a different Apple ID, you just need to copnfugre different Email address you can be reached at for the different devices.

Go to Settings->Facetime->You can be reached by Facetime At:

Remove your husband's email from there, and add a different one for each device.