iPad messaging problems
To solve the first part of your question, check this out:


  
  On the iPhone, go to Settings -> Messages -> Text Message Forwarding.
  This option will only appear when a compatible iOS or Mac device connected to the same Wi-Fi network.
  Your iPad should be listed in the Text Message Forwarding setup window. Set the slider to the on position to enable text message forwarding to the iPad. Enable Text Forwarding
  An authorization window should appear on the iPhone asking for a code.
  The code is available in a window that will appear on your iPad.
  Enter the code from the iPad into the authorization window on the iPhone. When the code is entered, this authorizes text messages to be forwarded to the iPad.
  You will now be able to send and receive SMS text messages on the iPad.
  


From the Apple Support Site:


  If your phone number isn't listed on an iPod touch or iPad, follow
  these steps:
  
  
  Update to the latest version of iOS.
  Verify that you're using the same Apple ID that you're using on your iPhone.
  On your iPad or iPod touch, sign out of your Apple ID in the following locations:
  
  
  Settings > Messages > Send &amp; Receive. Tap your Apple ID, then tap Sign Out.
  Settings > FaceTime. Tap your Apple ID, then tap Sign Out.
  
  Sign in to your Apple ID with FaceTime and iMessage.
  
  
  If your phone number still isn't listed, follow these steps: 
  
  
  Sign out of your Apple ID on all iOS devices, including your iPhone, in the following locations:
  
  
  Settings > Messages > Send &amp; Receive. Tap your Apple ID, then tap Sign Out.
  Settings > FaceTime. Tap your Apple ID, then tap Sign Out.
  
  Sign in to your Apple ID on your iPhone.
  When activation is complete, your Apple ID and all verified email addresses should be visible in Settings > Messages > Receive At and
  Settings > FaceTime.
  Sign in to your Apple ID on your other iOS devices.