see to it that中的it 是that后面引导的从句的形式主语吗?

完全正确!
see to it that中的it是that后面引导的从句的形式主语
You will see to it that your methods are ideal.
你将负责采用最理想的方法.
see that=see to it that“注意,务必,保证”
但是这是两种不同的结构.see that...这里that从句是see的宾语从句.
See that you spend it wisely.
注意别乱花这些钱.
欢迎探讨词法语法问题.