now that 可以直接代替as吗（now that和in that的用法区别）

不能，因为这两者意思是完全不同。now that中文意思是conj,既然

Now that you mention it , she did seem to be in a strange mood.既然你说到这事儿，她确实好像情绪不大对。

Now that she had him in her clutches , she wasn't going to let go.

她既然已经把他控制在自己手里，就不打算让他脱身。

now that （既然）是引导条件状语从句的, now that 之后是一个条件. as （因为）可以引导原因状语从句,as 之后是一个原因.