Can one recommendation letter from professor and two from internships help in MS applications?
As a general rule, I would take recommendations from people who worked with me directly. Then, I would look for people who were pleased by my performance. Third, I would take the recommendations most relevant to the position I'm applying for. 

It matters to some extent how famous is the person recommending you, but I think the graduate committee would be more interested in a letter coming from someone you worked with such as the assistant professor, the professor and CEO you did internships for. That letter is more likely to be more factual and tell the committee what you have actually done while working with those people. I would be happy to see in a student's application letter that they actually managed work teams. 

In your case, you don't have to ask people you only took classes with. I remember when I had to write recommendations for students who did well in my class. I still didn't know what to say beyond what I knew from their course work. I think they might have deserved better than that, but I couldn't offer more.