Well...I'd keep the Vicks off his chest and away from his face. It can actually irritate more than help at that age.
Otherwise, it sounds like you are doing just about everything you can. Sitting in the bathroom with a hot, steamy shower running every couple of hours may help.
Small amounts of caffeinated tea--the caffeine can help relax airways--with lemon (and honey if you feel comfortable with it at his age) may help ease it.
There are some homeopathic cough remedies that can help, but I don't think any of them are listed for children under two. I use one called Chestal that I find at HEB or Whole Foods. I found that it was more effective than what the doctor prescribed...even if it has to be taken more often.
My daughter also sleeps better on her stomach when she can't breathe or is coughing. Inclined but on her stomach...I spent many nights in a chair (recliner or with a stool) holding her so we could both get SOME sleep.
Good luck...just a couple more nights.