You will find that First Aid Step 3 is painful, though there are no good substitutes. UWorld is awesome. I cannot stress enough to do the CCS cases. Haresh will tell you otherwise. You are doing more than sufficient work, especially if you are doing a clinical internship (i.e. Not pathology).
I studied for about two weeks with Uworld only (having two free weekends really helped). I took it in my first month of internship. To give you an idea of what / where I was coming from:
248 Step 1 - Kaplan Course, 197 hours or whatever
252 Step 2 - Kaplan Course, 196 hours or whatever
233 Step 3 - Uworld Only
I share that to say that (A) I suppose I had a good foundation, but (and more importantly), (B) I was able to pass Step 3 and get an average score with doing minimal studying where I had previously spent far too long on a prepared course to barely scrape by an SD.
Bottom line, Step 3, not hard.