I'll take a stab at those, if you'll let me:
1) Eureka's wings were part of her evolution as a Coralian over the course of the series, so it wouldn't make much sense for her to lose them just like that simply because she was going to remain on Earth. The fact that she attained that distinctive look also helps to reinforce the whole "humans and Coralians living in harmony" concept. Plus, like you said, Renton likes them.
(As a side note, Renton's "Can I touch them?" wins my vote for the most innuendo-tastic line of the series.
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2) As the Nirvash said during her final speech to Renton and Eureka, half of the Scub Coral was departing the Earth to journey to the "tenth plane," in order to find a way for all humans and Coralians to live together in peace, without the threat of destruction. (Presumably, the Coralians also took with them the humans that had been absorbed by the Scub Coral, as we see images of Norbu, Sakuya, Adrock, and Diane receding with the Nirvash.) In an overview shot of Earth near the end of the episode, we can see that large portions of the Scub Coral have vanished, revealing the planet's original surface below. As Gonzy said, "there's no reason why there can't be more than one path to enlightenment;" the Scub Coral that left would be working in their own dimension to make cohabitation possible, just as Renton and Eureka would be on the Earth. As for Bellforest, it was presumably on one of the portions of the Scub Coral that remains; although the series doesn't specify, I'd assume that the Coralians had enough discretion to not destroy humanity's settlements, seeing as how they want to co-exist with them and all.
3) We don't get any specifics about the future of Holland, Talho, and the rest of Gekkostate, but considering the tone of the whole series, I think it's safe to say that Talho gives birth to a happy, bouncing baby, while Holland is going about trying to right the wrongs of his brother; I'd assume that the rest of Gekkostate is right there with him.
4) If you take another look at that shot, you'll notice Dominic, Anemone, and Gulliver sitting next to the motorbike and looking up at the moon.
5) It's true that the Super Izumo didn't have to do much in the end, but that's all the better for Jurgens and Co.; fortunately for them, the military was too occupied by the massive hordes of Antibodies to attack them.
We did see it fire off a few shots at one point, I believe.
6) I don't think that Jurgens necessarily gave the Gekko his entire fuel supply, and even if he had, I'm sure they were able to bum a lift from someone before too long. We do see Dominic and Anemone safe and sound at the end, after all.
7) If I had to guess, I'd say that those orbs were some sort of signal or stimulus to the Scub Coral to begin their journey to the tenth plane.
8) From what I've heard, the dub was just about exact to the original at that point. From the conversation between Axel and the kids, I'm fairly sure that Renton and Eureka hadn't returned yet. When Axel says to Maurice, "Out of all the members of this family who've ever left this town, your poppa was the only one to ever come back," he goes on to say, "The fact that I have three great-grandchildren here with me is proof of that." That second line leads me to believe that Renton and Eureka hadn't returned in person yet, but that, for Axel, the fact that the kids are there counts equally as Renton returning. (I'd assume that Holland dropped the kids off with Axel, seeing as how he was their only remaining family member.) All of that being said, and again, considering the theme of the entire series, I have no doubt and my mind that the two of them will return home before too long. (In fact, the final frame of the original Japanese broadcast of the final episode is a beautiful colored pencil sketch of Renton, Eureka, Axel, and the kids all standing together; this shot wasn't included on the Japanese DVD, so it's uncertain if it'll be on the American release.)
9) Like I said above, half of the Scub Coral is still on the planet, so I'd guess that the trapar waves are still there. The reffers need somewhere to lift, after all.
(Speaking of which, the cover art of the final volume of the Japanese DVD release shows a young brown-haired boy with green wings and a young green-haired girl standing with surfboards on a beach...maybe Renton and Eureka's kids will inject a bit of old-school into the reffing community.
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10) Who knows; they might give her some sort of advantage. If/when Gekkostate goes to play that team again, they'll need all the help they can get.
