Quote: He feels I can be and frequently am “strained and formal,” whereas with his (mostly 20-something F) friends, he can be “childlike and innocent.” This is what keeps him from fully integrating me with them, because he doesn’t want to introduce strained and formal into his repertoire with his friends.
You know what I think? This is just so much alien BS. In future years he will deny ever having said this to you.
For "childlike and innocent" just substitute "immature and irresponsible" as in "I don't want to grow up, and being with a woman who is a full adult makes me nervous".
Honestly - if I thought you were a stick-in-the-mud, I would call you on it, because all our WASs need us to be more playful and relaxed. But seriously - this is HIS problem, not yours.
Hey - don't you like the part where you told him (calmly) your needs - that you would like him to spend more time at your place - and how he heard you and decided to come over later and meet that need? It's amazing the power of simply stating what you want without all the attached drama of insisting they must meet your request.