I'm just a fellow applicant, so take this with it's commensurate grain of salt. I did score very well, for what it's worth.
1) I would buy more books - I had a few and did all the practice tests more than once.
2) No. Aptitude, verbal, and quant are just as (if not more) important as far as I know.
3) I didn't really study for the aviation section because I'd already passed the PPL FAA test and it's all similar. I would just review whatever stuff you used for the FAA test.
4) I would pick up a reading hobby with some more challenging books. This is just a general life tip, as well. You will pick up a lot of vocabulary surprisingly quickly (and without trying to) by just reading good books 30-60 minutes a day. FWIW, I found most of the test to be nearly identical to the Barron's book I started with.