[minminRW]

KyleGoetz,
On first example,
名詞になる and 名詞となる are almost same meaning and interchangeable.
名詞となる is used in limited situation such as writing or official situation.
名詞になる can use in any situation.

Second example,
嬉しくなる is OK,
嬉しいとなる (or 嬉しいになる) is NG.
It should be 嬉しいと思う or 嬉しいと感じる.
It is because of collocation, you should memorize with no reason.