Nava- how did the show go?
KKH-He probably can stay in the coop from now on.. but if below freezing night is forecast within the week or 2, would bring him in for the night just to be on the safe side. Past 2 weeks of being in the coop he should be completely acclimated. His brothers/sisters have been outside already but then it's much warmer/milder here- days high 70/low 80s nights were mid 40s when I moved them out.. currently going thru a chill, last night it went down to 33 & it's 50 as I write this.
As for growth, should start seeing one soon if not already. Looks like his body had filled out some. His grandfather was very, very small, several of his(your boy) aunts/uncles/potential parents were smallish. If he's going to be on the smaller side, might be just about the size of your bantam hen(she was one of the biggest ones) when fully grown.