关于下面这段英文叙述，我有几个语法问题请高手帮忙解答一下，万分感谢

Question

although the archaeological evidence shows that cattle and sheep would have been the most common farm animals,it is known that pigs were also kept.the animals would have aided the family,not only with heavt farm labour,in the case of the cattle,such as the ploughing of crop field,but also as a valuable from of wool or hide,and food products.
这段陈述中一直在使用would have过去将来完成时，这是设么意思啊，为什么不直接用过去将来时呢，还有but also as a valuable from of wool or hide,and food products中的from of 是什么用法阿

Answer 1

1.情态动词+完成时态，其实正确来说就是would have done,意思是，本可能。。。本来会。。结果就是没有，表示假设。比如文理的，would have been the most common farm animal，。牛和羊本来也将变成最平常的。。。（就是说，实际上没有变成最寻常的家畜，如，猪）
第二个问题，你是不是看错或者是卷子印错了，from和of 同为介词，不肯能那样用的，valuable后面一定是名词，所以应该是form，方式，形式。“但是同样作为一种有价值的形式。。”