Reading texts out loud (while driving, for example)

Have you verified that audio recording for voice commands is enabled over bluetooth ?

It's sort of buried. Here's how I found it on my Pixel XL: Say OK Google, when the card comes up tap blue the tray on the upper right corner, on the next screen tap the 3-dot menu on the upper right, select settings, under "Devices" select your Pixel, then scroll to "Other Voice Settings" and find "Bluetooth Headset" option and turn it on.
Yes in did verify voice commands over Bluetooth.
In also went through all the settings under Pixel as you recommended and verified all was set correctly. Still can't get messages over car audio. When I use BT headphones I click the talk button that activated ok Google and say read my messages/texts which then says you have 5 recent messages do you want me to read them to you? I follow the prompts to read or ship the last 5 messages/texts.
It will not work on my car BT.
 
Assistant has matured over time. I've ditched Drivemode because I was getting inconsistent results with trying to give voice commands to it (I suspect it was the result of my car's audio system, there was a delay between when the device was actually listening and when I was given an audible cue to speak).

With Assistant I'm able to listen to texts just fine as long as I know they've come in - my notification on my fitness watch is how I can normally tell, otherwise I rely on the sound of the notification chime. Once I know that I've got a text message I either press my voice command button on my steering wheel or I say "Ok Google" to bring up Assistant. Conversation basically can go like this:

me: Ok Google
(audible prompt):
me: "What's my last message?"
assistant: "You have one last text message, its from ____, do you want to hear it?"
me: "Yes."
assistant: "It says ______, do you want to reply, repeat it, or is that it for now?"

At that point I can ask assistant to reply, to repeat the message to me or say "That's it." to end.

If I ask assistant to reply it will dictate my message but it won't repeat it to me, instead it will just say "Got it. Do you want to send it or change it?" at which point I can say "What does it say?" . . Assistant will then read the message to me and ask if I want to send it or change it, which I can do via voice commands (or I can even say cancel).

I actually use google assistant for the same thing in my car but when I reply it will say "here's your message to_______ do you want to send it or change it?" but mine reads the message back to me.
 
"Google Assistant is now able to read your SMS messages back to you.

SMS-enabled Facebook Messenger or Hangouts messages may also be read by the intelligent assistant. Say “Do I have any messages?” or “Show me my last message” and Google Assistant will read back your most recent text messages."
 
I just convinced my husband to give up his Droid Maxx so that he would have wifi calling (we have a house where VZW barely has service) and I just assumed that Google Assistant would have the ability to read and respond to texts hands free. As Ry reports, his Motorola would detect that he was driving and announce text messages. He could ask it to read, and then he could respond. It was by far his favorite feature on the phone. This did not involve bluetooth, which is important, since his truck does not have bluetooth. I understand that the phone probably won't detect the fact that he is driving, but if if could at least read and respond to messages without him having to touch the phone, that might satisfy him. Otherwise, we may be back to the drawing board.

He is not someone who is willing to tinker with his phone at all. I need to solve this, if I want him to "like" his new phone. Will Google Assistant read texts if asked or not? There seems to be some conflicting advice here.

MOTO is really the best but on a non Motorola phone I recommend Dragon Assistant. It does the same thing that the drive mode of MOTO does - reads and replied to text messages and announces incoming calls with hands free answer.