How can I politely tell a student that I already support him several times and that is enough?
I'll assume you already have language that indicates your support. Don't give up on that.
But, ask him for two things. First, that he only asks for feedback once a week (or whatever you are comfortable with) and add a report on changes and why they were made.
Second, ask him to specify in the report things he is unsure about and to detail why he is unsure.
The goal is to get him to think more deeply about why he is doing things and to separate the simpler from the deeper things.