My husband just got a new iPhone, I used my Apple ID for his phone, now our texts are shared and contacts , etc

You are welcome. Sync the phones to get all data on both phones.

If you are going to create a new ID for him to use on his phone, turn off Optimization on his phone. Since it is a phone, turn off Optimization in Settings/Your Name/iCloud/Photos.

You shouldn't need to do another backup, although it won't hurt anything.

Other than making sure Photos Optimization is off before changing the ID, you do not need to adjust any other iCloud settings.

After making the ID change on his phone, if you are still missing contacts on your phone, got to iCloud.com/Account Settings using a computer browser using your Apple ID. Under Advanced at the bottom left, select Restore Contacts.

You can if you don't mind seeing what you are seeing. Apple IDs aren't meant to be shared. I suggest you create a new ID for his phone to keep your data separate. When changing to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. Also set up Family Sharing to keep access to your apps/purchases. 

Apple ID - create a new

Apple ID – Create

How to transfer all files from one iCloud account to another

 Apple ID email address or password - What to do after you change

Family Sharing

Family Sharing - Set up