>then how would one endeavor to live life as if he has free will?

You can't.

The more interesting question is, how does it look like to endeavor to live life as if you have free will? And the answer is going to be different from person to person, so the question you asked is completely hopeless ;)

>Here's the problem - this lack of free will implies none of us have true moral responsibility for our actions

This is true but you can connect consequences to certain actions regardless of being a free will agent or not.

>and operating according to this assumption is detrimental to both individuals and society.

And therefore this is also false because there are consequences to actions regardless of free will. In nature as well as the man made world.

And this is essentially what we have done with our laws. None of us have true moral responsibility for our actions, but we hold people responsible nonetheless, because the alternative would be worse. Most people just don't realize this.

Where this gets more complicated is if I created a self-conscious killer AI. Does he deserve the consequences for his killings or do I? And if we loop back to what I explained above we get into a problem, because the only difference between a killer AI & a human murderer is that in the second example I engineered this robot and the person was engineered by 'circumstances'. Of course, so was the engineer of the AI...

>Exactly how we did up until now.

I think this is right. Because regardless of free will existing, consequences do exist.

So regardless of taking an action with free will existing or not in the back of your mind, the consequence will be the same and therefore there is no difference.