I'm not saying that you need to be gentler with him, I'm sure you're doing your best to be kind. But people can often sense, even subconsciously, how you feel about them, which will obviously color things... and your words here are very negative, which doesn't seem like a good sign. Maybe that's just you venting and doesn't reflect how you really feel -- which is cool, it's important to have a place to vent safely -- OR maybe you really do look down on him and that's making things harder... for BOTH of you, really, because for you it means you're abiding by a rule you dont like put in place by someone you don't respect, which is gonna be harder to follow than a rule requested by someone you DO respect.
So, yeah, I could be totally off-base. But rather than trying to treat him differently (which, if your thoughts stay the same, would just mean being fake, which most people can pick up on), I would just suggest really trying to put yourself in his shoes, really imagining how you might have felt if your wife had always given you less cause to feel secure and satisfied in your marriage, and you had never once thought of non-monogamy, until suddenly you find out she's in love/lust with your best friend and needs HIM to be happy and turned on. Yikes. Anyone would need time to adjust, time to be a little scared and sad and unsure, time to come to trust that no one involved is looking to make a fool of you (which is just what you were proposing to do in your first post!).
Remember, three months is really no time at all when it comes to making an adjustment like that... though of course it feels like an eternity to two people newly in love! Your reality and his are very different right now.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.