There are many doctors saying now that dairy at all in children so young is not good, and, is a leading cause of many allergies / colds, etc.
I would definitely eliminate those as suggested below until he is better.
Me, after my first stayed sick with neverending colds, completely took out dairy, and, gave her strictly soy products until she was 3.
To make up for the Vitamin D and calcium that so many worry about, we gave her vitamins every day. They make liquid vitamins for the little ones that are not ready for the chewables or the gummies.
This is the best home remedy I can suggest, you might be suprised how quickly he gets better, assuming that he is having dairy of course!
Even now that she is 8, and, my youngest is 4, we do not have much dairy.
The extent of our dairy is fat free, organic milk for cereal (not every day), shredded cheese as occassional toppings, and, the occassional fat free yogurt. My kids probably get about a cup of dairy a week. We do take the vitamins regularly though, and, now that they are older, we get the juices with the added vitamin D and calcium, along with anything else I can get that has the added vitamin D and calcium.
If he is not on any dairy, I second the saline sprays to help clean out his passages, that works wonders! They also make lollipops that he can suck on to sooth his throat, (with your supervision of course!).
Pedialyte (they have drinks and popsicles), is great for liquids if he is not getting enough. As long as he is wetting his diapers regularly though, I would not worry about the liquids.