Got new phones, iMessage not right between the two

Both my husband and I upgraded to the iPhone 16 pro. Since doing so, when we text each other it is putting us in a group text, saying that it is my husbands phone number, contact and myself. We have also lost chunks of our messages from morning to afternoon, iMessage turns off and goes to SMS and I cannot text him. This is only happening between our two phones and no other contacts. I have tried deleting his contact all together, deleting our messages and starting over, only turning on receiving and sending texts from our phone numbers, turning iMessage off for a couple min and turning back on, restarting our devices and turning our iCloud’s on and off. Everything that used to be seamless between devices such as phone to iPad or phone to mac computer or CarPlay has been anything but and I am so frustrated. Any advice??