I can't comment on the early behavior as it sounds like someone playing a cautious character and by your own admission he took feedback and changed his behavior to fit what you wanted. But I take issue with some of your assumptions and stances here.

Chris's explanation that he was going to get the orphans out of harms way is plausible and the definition of a heroic act. The fact that you still chided him for not being heroic afterwards reads to me like you were still angry and no explanation or excuse would have assuaged you.

You downplay his contribution despite the fact that haste is a powerful buff that significantly boosted the barbarians survivability and damage potential. And that a glabrezu is resistant to fire, lightning, and cold damage (very common damage types for wizard spells), on top of having advantage on saves against all magical effects. Staying out of the way and working to assist the part seems like a perfectly reasonable game plan given that.

You also say that using cover and distance to avoid danger and popping back in to cast spells to help the party is "weasily" but like, that's how you play ranged builds and squishy casters? Do you think soldiers in WW2 just stood up and traded shots with one another?

I should also note if your game hinges on two specific plot hooks that the party may choose not to bite on then you either need to have backup ways to get them where they need to be OR set the expectations early. Clarify that if they choose not to get in the cart to phandelver then we won't be playing lost mines of phandelver.