Hello,
I think the strength of a candidate rests in the well-roundedness of an application, for the exception of the Step 1 score which can be used as a screening tool by residency programs--which you did well on. If you are strong on the whole, I don't think one single factor will make or break your application--but I understand the anxiety you are experiencing headed into the great unknown of applying for residency. Make sure you have extracurriculars demonstrating your interest in Peds and Medicine (I was active in the Peds Interest Group and also saw adult patients at a walk in clinic). Also, while the Personal Statement isn't the most important thing, it can certainly bolster your application by showing your humanistic side and your ability to work with others. Once you get to an interview, I really think that they are evaluating whether or not you are someone that is likeable and a team player. At that point, you have already proven to them that you are strong academically. So your goal is to get pass that round onto the interview.
Two things that I highly recommend doing to put your mind at ease and further increase your chances of obtaining an interview. One, take your Sub-I early in Peds and do well on it. If you can do it in the PICU, it really looks like you are stepping up to the plate and taking the most challenging rotation. Get a glowing letter of recommendation from one of those Attendings.
Two, consider taking Step II early. If you did well on Step I, you are a good board test taker. I was sure that I was going to go down after having 240 on Step I and people advised me to put off Step II as long as possible. But, I didn't and actually went up by 10 points and I waited probably longer than I should have to take them. You are freshest after your 3rd year clerkships. My school has a deadline for taking Step II by January, so residency programs are probably going to see them soon or later, unless you block their release--which I personally don't think is a good idea. You should never leave a residency program with a question in their mind about your candidacy, give them as much information as possible. If you take Step II early and do well on it--which I presume you will do if you study an ounce like Step I--then that casts any doubt in a program's mind that you will pass both boards.
This is just advice from someone who has just gone through the process, but feel free to PM me with any further questions you may have!