I have taken both Stats and Chem I. I found both of them to be quite manageable; Intro to Stats is basically just a combination of formulas and some basic knowledge of how probability works, and Chem I is a combination of memorization & formulas, but not tough if you do the homework. Lab is also not tough. However, it does depend on your type of learning style. I find that some people excel in chemistry and find biology really hard for example (that's my type), whereas some people are better at memorization and chemistry bewilders them. You won't know 'till you try.
From everyone I talk to about Calc II, it really IS hard. I have friends who got into Calc II and have never made lower than a B on a math test before, and are struggling to pass. But I do think that your courseload is manageable. It's good that you're only taking 3 courses, you'll be able to do it without stressing if you are a good student and don't just expect to study the night before for your tests.
Edit: Also, just as a note, when I took Stats and Chem I, they were in the same semester, and I had another math class as well as an economics class, and worked part time. It was not too hard. I'm sure you can do it too :D