"Idę" points to continuous, present action whereas "chodzę" reffers to present simple form. "Chodzę" could be continuous but it's informal and often goes with "sobie" - "chodzę sobie", where "sobie" doesn't mean much, it can be roughly translated to "just". (I'm just walking around).
Go! = "Ruszaj!", "Idź!" (commonly used imperative forms). Let's go! = "Ruszajmy!", but also "Chodźmy!" not "Idźmy".
Other sentences have made it look as if idę is closer to I am walking. Is that right?
My impression is that it generally means "I'm going" or even "I'm coming", technically on foot, but not necessarily so. For example:
At the end of the working day - "Idę do domu" - "I'm going home", which might well involve taking the tram. But once in the tram it's "jadę (tramwajem)".
You call to someone to hurry up as you're about to leave, or tell them that dinner's ready - "Już idę" - "I'm just coming" (like "Ja voy" in Spanish).
If somebody asks how you are getting home and the answer is "I'm walking", then I think Poles would probably say "Idę pieszo" ("I'm going on foot").
Yes. You uses "idę" while you go and "chodzę" when you do it for example every day ;)
Idę could be correct, if this was a first person narrative written in the present tense. I think 'I walk' is accepted for 'я иду' on the Russian course, probably for this reason. I can understand why they would be strictly separated, though, for didactic reasons.