英语长难句分析请帮忙分析这句长句.If its message were confined merely to info

英语长难句分析
请帮忙分析这句长句.If its message were confined merely to information and that in itself would be difficult if not impossible to achieve,for even a detail such as the choice of the color of a shirt is subtly persuasive-advertising would be so boring that no one wound pay any attention.
中文意思我知道,就想知道这句话的结构怎么分析,谁是谁的从句,修饰的又是谁?
还有.为什么 and that in itself would be difficult 后面又有一个if not impossible to achieve?
if后面不是加句子的吗?这个if和句子开头的if什么关系,如果有两个从句不是应该也有两个主句即两个谓语的吗?
后半句（从for even开始）,哪里是主语?谓语?
问题有些多,谢谢回答的朋友(⊙o⊙)哦!

查找了一些网络资料,发现这个句子有一点问题,现更改如下：
If its message were confined merely to information—and that in itself would be difficult if not impossible to achieve, for even a detail such as the choice of the color of a shirt is subtly persuasive—advertising would be so boring that no one would pay any attention.
修改地方：
information-and修改为information—and
persuasive-advertising这里并不是连字符,而是破折号,修改之后for even后面的句子结构就清晰了.
wound应改为would
这个句子选自《商务英语综合教程》的一篇阅读：
Money spent on advertising is money spent as well as any I know of. It serves directly to assist a rapid distribution of goods at reasonable prices, thereby establishing a firm home market and so making it possible to provide for export at competitive prices. By drawing attention to new ideas it helps enormously to raise standards of living. By helping to increase demand it ensures an increased need for labor, and is therefore an effective way to fight unemployment. It lowers the costs of many services: without advertisements your daily newspaper would cost four times as much, the price of your television license would need to be doubled, and travel by bus or tube would cost percent more.
And perhaps most important of all, advertising provides a guarantee of reasonable value in the products and services you buy. Apart from the fact that twenty-seven Acts of Parliament govern the terms of advertising, no regular advertiser dare promote a product that fails to live up to the promise of his advertisements. He might fool some people for a little while through misleading advertising. He will not do so for long, for mercifully the public has the good sense not to buy the inferior article more than once. If you see an article consistently advertised, it is the surest proof I know that the article does what is claimed for it, and that it represents good value.
Advertising does more for the material benefit of the community than any other force I can think of.
There is one more point I feel I ought to touch on. Recently I heard a well-known television personality declare that he was against advertising because it persuades rather than informs. He was drawing excessively fine distinctions. Of course advertising seeks to persuade.
If its message were confined merely to information—and that in itself would be difficult if not impossible to achieve, for even a detail such as the choice of the color of a shirt is subtly persuasive—advertising would be so boring that no one would pay any attention. But perhaps that is what the well-know television personality wants.
[结构]
If its message were confined merely to information—and that in itself would be difficult if not impossible to achieve, for even a detail such as the choice of the color of a shirt is subtly persuasive—advertising would be so boring that no one would pay any attention.
if引导条件状语从句,"its message were confined merely to information and that in itself would be difficult if not impossible to achieve"表示条件,
"advertising would be so boring that no one would pay any attention"表示结果,
"for even a detail such as the choice of the color of a shirt is subtly persuasive"作为插入语表示原因.
联系上文,its指广告的,that指its message were confined merely to information.
"and that in itself would be difficult if not impossible to achieve"
that in itself would be difficult就广告而言,(广告的信息只被局限于告知)也是非常难做的
if (that is) not impossible to achieve指如果(广告的信息只被局限于告知)不是完全不可能达到的
[词义]：
be confined to somebody/something: to exist in or affect only a particular place or group
The risk of infection is confined to medical personnel.
[译文]：
如果广告的信息只被局限于告知——如果这不是完全不可能达到的,就广告而言,这也是非常难做的,因为即便是一个诸如衬衫颜色的选择这样的细节都会具有微妙的说服意味,那么广告就会十分乏味以至于没有人会关注它.