Hmm. The House of the Wing is one of the Great Houses of Gondolin, bearing a white wing as their symbol, so... #6 (HOUSE OF THE) TREE?
And oh, wait: there's another double drowning, when Ecthelion went balrog-swimming. So either ECTHELION or FOUNTAIN for #3?
The Houses of Gondolin are really interesting, from a political speculation viewpoint. They were clearly founded after the city, since there's nothing like them anywhere else in Arda. How many were there originally? The Pillar and Tower were clearly once a single House - how did they get so large? The Wing is an obvious political fiction, and was the Mole even officially approved? It kind of feels like Maeglin took up with the miners (who as low-class workers probably weren't in a House at all) and started using the name.
So were they all craft-houses originally? The Swallow still bear an arrowhead, and the Harp a... well, harp (so was Salgant actually just a bard whose House had turned themselves into warriors in his despite?). The Hammer was obviously the smiths, who later became the Hammer of Wrath. Pillar-Tower could be the gate-guards? But this leads us to the idea of the Tree as foresters, the Fountain as engineers, and the Heavenly Arch as... well, rich cloud-watchers, which pretty much checks out.
Anyway, that's all off-topic.
hS