Think the first one that legitimately threw me for a loop was "Cat Fingers," but I think the one that first tugged my feels was, like for most people, "So May Birthdays"
(especially when Garnet's just brutally honest at the end and basically goes "let's face it, we are way out of our depth and have no idea what we're doing but we're gonna keep trying this whole parent thing" )
Oh man that show just consistently tops itself for me. Anything that focuses on pearl and amethyst's relationship or Steven and rose is a surefire way to break my heart
And of course the purple puma episode.
And all those episodes you've already listed.