I'm an OB RN (I mostly do post-partum). FWIW, I've never seen J&J Baby shampoo used at my facility or the other 2 hospitals I've been in,, but all facilities are a bit different.
I read your letter. I thought it was fine but wanted to suggest two things. First of all, the hospital has no control over what your doctor does really. They aren't in control of when or if he breaks your water. So I'd leave that part out. If that was an issue, you need to write a letter to him/her at his/her office.
Also, the part about notifying J&J about misuse by their facility - I'd change that.
Maybe just include something like "I don't see where on the shampoo bottle it is appropriate for internal use" (although some docs [pedis & opthamologists] recommend washing eyes out w/ baby shampoo sometimes if one has an infection). Anyway, wording it like that sounds less threatening than the other way.
I would send at least two letters - one to the L&D manager and one to the Department head of all of Women & Children's services (this will be L&D's manager's boss). This will certainly get their attention. Often times hospitals will send out patient satisfaction surveys. If you get one of these, make sure you include info about your stay as well.
I think your complaints will be taken seriously and at the very least I'm sure L&D manager will discuss at a staff meeting how negative attitudes and inappropriate comments reflect poorly with overall patient satisfaction (trust me, our dept. head ALWAYS tells us of postive & negative feedback). But you may also want to include something positive in your letter too, like if your discharge nurse was nice or if the nursery nurse was good. Anything that lets them know you're not writing just to complain for the sake of complaining will make your letter be taken a bit more seriously.
And if there is ever any doubt about what was done to you, at any point during your care, you are always entitled to view your medical record. Hospital's usually keep records on file at least one year before they send them off to be stored. The rude nurse should have documented in your nursing progress notes what she was washing you with and why.
I'm so sorry you had a bad experience. I work in a hospital and I've birthed in a hospital. I've also birthed at home with midwives. The homebirth was much more friendly and relaxed!