I wouldn't trust you as far as I could throw you.

我尽量形象地回答你的问题：

1.  句中出现了would 和 could，不一定就表示“虚拟语气”。不要一见到这两个词，就必言“虚拟”。在一定的语境里，它们还可以表示说话人的“委婉” 和 “意愿”。本句便是此种用法。

2.  这个句子本身，就是一个含有比较从句的主从句。as...as... 结构是修饰 trust 的，说明“信任的程度如何”。

信任的程度是：as far as I could throw you 指“我把你推出去，甩出去，扔出去的距离”。可想而知，这个距离仅仅是 a bit （一点点）。

3.  这个句子存在否定转移。即：not 实际否定 as...as... 这个程度。意思是说：“我信任你，但程度是 not as far as I could throw you”。 此时，网友应该想到了这个词组：not a bit。

I wouldn't trust you as far as I could throw you. =

I would trust you not as far as I could throw you. =

I wouldn't trust you a bit.

not a bit（一点也不）

4.  I wouldn't trust you as far as I could throw you.

【翻译】我根本不信任你。  我一点也不信任你。