To say that Mr. Zhou was "losing his wife and breaking down", i would be an understatement. If it weren't for his girlfriend's getting in trouble, it is estimspeculated that these dozens of boxes of Maotai would not have not been discovered by the police.

To say that ____ would be an understatement 是一个常见的句型，意思是这么描述一件事情不能足够显示它的程度。
estimate通常会用来估计时间或数量。

But now that this illegal thingdeed has been done, you must understand that somethingthere's no going back. As such, it's important to not take chances since crimes will be discovered sooner or later, and don't take a chance.

“thing” 其实没错，但deed和“行为”更相关，会比thing更正式。

不能突然用“you“，因为整个文章是第三人称。:)

我把故事的寓意写成了单独的句子。As such 会比 so 高级点！