#1 already exists: the “hide ignored tags” checkbox in the right sidebar of the main page and the
/questions page, also present in your profile in the “prefs” tab.
#2, #3 and #4 are unlikely to be implemented in the Stack Exchange network in general, given how Stack Overflow users often obsess about reputation. (For example, there's no easy way to see the upvote/downvote breakdown if you have less than 1000 reputation, and that's a common feature request.)
Regarding #5, the idea of closed questions is that they are in one of three states:
- recently closed questions which might be considered for reopening, so they shouldn't be ignored.
- old closed questions that no one cares about any more, so they should be deleted.
- differently-worded duplicates that deserve the same billing as the non-closed duplicate.
I haven't been following CSTheory much, are there a lot of closed (and not migrated) questions? Maybe there should be a policy of deleting closed questions after a while? (Takes 3 votes from users with 10k reputation, which in practice means only moderators can delete questions.) Note that I'm just reminding of the possibility, I don't know if the policy would be good for CSTheory. A point in favor of deleting is that closed questions can give a wrong idea of the site (e.g. if most of the questions in a tag are closed, the tag looks more important than it should — and simply being there, because not everyone, especially visitors reaching the site from Google, pays attention to the closed status). Another point in favor of deleting off-topic questions is that the answers are often suspect because they haven't reached experts — but in CSTheory's case this may not apply so much, if the off-topic questions tend to be too elementary but nonetheless satisfactorily answered. A point against deletion is that closed questions can still have useful answers; an intermediate policy is to delete closed questions when it becomes clear that they haven't been reopened, unless they have answers with useful content.