Is it okay for a 15 to date 22?
If dating includes sex (or any form of sexual activity) then the answer is yes - and parental approval is irrelevant. If you are under 16 then you may not lawfully engage in any sexual activity (not just intercourse) with anyone.
Is it wrong for a 15-year-old to be with a 17 year old?
People of any age can date each other. If either of them are under age their parents have to agree to the dating. It is never illegal to date with parental approval.
Is it weird if a 17 year old dates a 15-year-old?
Yes, its perfectly legal for a male of 15, and a female of 17 to date. You both are still minors, but until said person becomes 18, it would be illegal for said people to involve in a sexual intercourse.