1. 倾向于把现在分词词组meaning it has fourteen lines解释为this poem is a sonnet的句子状语,语意上现在分词词组是对这一分句内容的补充说明,根据语意角度,姑且把现在分词词组解释为补充性状语。似乎《剑桥英语语法》将其解释为补充语。
2. 并列关系应该是这样:……,this poem is a sonnet, is written in iambic pentameter, and follows a specific rhyme scheme.
仅供参考。