We are planning to 'save' some of the Houses of Gondolin for later in the story. Obviously, the House of the Mole needs to wait for Maeglin to arrive in Gondolin (Season 5), and the House of the Wing needs Tuor (Season...8? 9?). Rhogrin (Rog) will arrive in Gondolin post-Nirnaeth Arnoediad, and thus the House of the Hammer of Wrath will likely be made up of mostly non-Gondolindrim who returned to Gondolin in the aftermath of the battle (those followers of Fingolfin/Fingon are likely the ones who are acknowledging Turgon as High King, so...there's that). So, that will likely be a Season 7 thing.
Most of the Sindar are dark-haired, so Galdor being dark-haired checks out. Character economy suggests that Galdor of the Havens and Galdor of Gondolin should be the same person (especially since we've already introduced him and established that he's alive in the First Age). We can show him pining for the Sea in Gondolin, and thus not leave Aredhel alone in her restlessness. Having him escape the destruction of Gondolin with Tuor and Idril would be fine. I do agree, though, that he'll need Círdan's 'blessing' to join Turgon's people. In Season 4, we have some of the Falathrim join Turgon at Vinyamar, and thus there is a conversation between Turgon and Círdan about that in Episode 4 (Of Beleriand and Its Realms), in which Círdan is basically asking for permission for his people to move into Nevrast. We also have Galdor serving as messenger between Círdan and Turgon in Ep 9 (Dagor Aglareb), which ends with both of them arriving with aid to save the city of Vinyamar.
I think Galdor, though a minor character, can be our prime example of a Sinda who accepts that the Kinslaying happened, but that not all of the Noldor are guilty. So, once it comes out that Turgon wasn't even in Alqualondë when it happened, it should be easy enough for there to be some sort of reconciliation there. And Galdor should definitely have a private conversation with Círdan before they move to Gondolin, in which he seeks (and gets) approval to lead the Sindar under Turgon. Having him rejoin Círdan after the sack of the Havens of Sirion should be fairly organic.
I did suggest a backstory for Penlod. It was my suggestion that the reason for two houses is that he has a dead/missing brother who was 'meant' to lead the other house. That brother could die in a number of ways - crossing the Helcaraxë, defending Vinyamar during the Dagor Aglareb, during the construction of one of the cities (hey, construction on that scale is dangerous), or being taken captive by Sauron. It was vetoed that 'Penlod's brother' be one of our 4 named captives, so certainly there wouldn't be any focus on this story. But, that doesn't mean that some explanation for two houses, one lord couldn't ever come up in conversation, so I don't think the idea was vetoed so much as the desire to tell that story in any detail was. If anyone has any alternative suggestions as to why there are two houses with only one lord, we can certainly entertain them. To my knowledge, Tolkien never suggested an explanation as to why there are two houses under Penlod.
The most obvious alternative is that one house is primarily Noldor, and the other is primarily Sindar. This works well with Penlod marrying a Sinda woman, and their child being Pengolodh.
Or, of course, we could do 'all of the above', should the need to explain the situation ever arise.