I think he was in actual "fear" from the time Maggie arrived back, to the present time he spent at that house. The snark, I think, meant "I'm not gonna be in fear now. I'm determined to work out a way to live among this group and prove myself. Maggie will be the biggest obstacle, and I'm not gonna fear what the outcome is."
Just my imagined thought on it. I took the grin as - I'm willing to be friends, for real, IF it's possible.