So in 2x04 Stuck - only the fourth episode of Eddie - we have
Buck asking why Eddie doesn't date. (Testing the waters there Buck? 😉)
Buck being the one team member who follows Eddie into the hospital and meets members of Eddie's extended family. We didn't see their exit from the truck, but at this point Eddie doesn't seem at all phased that Buck is with him.
When Christopher is at the station due to lack of childcare and Bobby comes over, Buck has already told Bobby that it'd happen and it's all cleared.
Buck reels off all this information to Maddie that he's picked up about Eddie's situation with Chris and finding suitable childcare. He's had a long conversation with Pepa by the sound of it.
Buck pretty much gushing to Maddie about Christopher and Eddie.
The "boy crush on Eddie" line.
Buck being his fix it self and introducing Eddie to Carla. This small act has such an impact on Eddie's life going forwards.
I think that here we have Eddie experiencing the result of saying that Buck can have his back a couple of episodes back.
And we end with Buck starting to come to the realisation that it's time to leave Abby in the past.