Text Messages instead of iMessage Irritation!

I have an iPhone 15 running iOS 18.2.1. My husband has an iPhone 13 Pro running iOS 18.2.1.

For the past week, when I go to send him a message in Messages, instead of saying "iMessage," the blank says "Text Message SMS." Sometimes I can get around this by going to Contact rather than through Messages to send the message. Messages has decided of its own accord to treat the conversation as a group message between his phone number, his email, and my phone number.

"Text Message SMS" go to his email, not to his Messages.

These are things I have tried after scouring various troubleshooting posts:

• • Updating my iPhone
  • Updating his iPhone
  • Turning phone on and off
  • Turning iMessages on and off
  • Turning his iMessages on and off
  • Verifying that he can only send and receive iMessages from phone number, not email (checked multiple times)
  • Turning off iMessages, restarting phone, turning iMessage back on
  • Signing out of iCloud
  • Signing out of iCloud, restarting phone, signing in to iCloud again
  • He has signed out of iCloud and signed in to iCloud again
  • Deleting husband as contact, using just his phone number, adding him as contact again
  • Deleting husband’s email from contact and just having his phone number
  • Deleting his contact and entire message thread and starting new one with just his phone number (my phone remembered it and thread history despite the deletions)
  • Blocking his email address -- even after blocking, it still sent the text to his email

Notably, under “Send Message” written link in his Contact (the part you scroll down to), the default was his email, not his phone.

The only thing I can think that preceded this was that I invited him to share passwords in the Passwords app. I deleted the invitation and thought that solved the problem. It did not.

Any time I try to send him a message through Messages - even if his email address is deleted from his Contact in my phone or even blocked from my phone - my phone tries to send the message as a Text Message SMS. I don't want to have to send him messages through Contacts. I don't want our text thread treated as a group message between his number, my number, and his email.

This is driving me insane. It doesn't happen with my other contacts. Just him.