I do not miss it, it's just a bit different and also their style changed a bit. And we won't get it back anyway so no point in missing it, I love her voice nowadays too. Unless I missed an information about it, she simply forced her voice too much and didn't rest it/trained it enough so she got problems.2.
Depends to what/who you compare them to. Compared to some huge stars they are small but I think they have a good fan base. Not all the bands can do Budokan or OJH and this year they have 3 more arenas. They are obviously not #1 but they are up there.3.
This is a bit like #2. They are not superstars but they sell good/ok, much much more than some bands but less than others. I also wish they would sell more but I think the important part is that their sales are not dropping at all and also it seems their company supports them a lot lately because the girls can compose more music it seems and also they are doing 3 arenas. So maybe they don't get only #1 releases but they are always in that top 5 I think.
Also I think the sales numbers we have for SCANDAL are only the numbers of physical CD sales not digital? Anyways, it's not like in the past, 60.000 maybe doesn't sound too big but it's still a lot. I'm listening to Ayumi Hamasaki lately and she is a mega superstar in Japan. In 2004 her album My Story sold for 1.1 million (source Wiki). In 2012 her album Party Queen sold "only" for 148.000. So a mega star sells for 148k, SCANDAL for ~60k, I think that's nice. In 2013 her album Love Again sold for... 88.000. Yeah I know it's hard to compare and there can be a lot of reasons for the numbers but just wanted to point that out 4.
They were in the same dance & vocal school called CALESS, it's not a normal high school if I understood correctly. That's why they don't have the same age.5.
We will never know
They talked about it because they are professionals and you have to think about all the possibilities but in the end they didn't do it. To me, SCANDAL is a perfect set up and I cannot imagine the band without HARUNA. When she had problems I doubt they could have performed with only 3 members, not only is HARU the main singer/leader but she also plays guitar and this is not just an idol dancing band. Would have felt very weird to see them without HARU.
And for future it seems HARU now takes care about her voice like any other singer so it should be fine. If she has a problem I guess they will simply change the schedule and not perform but instead maybe work on songs in studios or things like that. I can't see SCANDAL without HARU to be honest.
By the way, you should find all the information you need on Heaven now for the future ^^ There is a special media section only available to members with more than 50 messages too. But don't spam or mods will ban you xD