I wish I could help you, I know how frustrating it is. Otis is a runny nose too. Thick, green mucousy snots running down his nose... sometimes. It's not all the time, couple times a day at most. Doctor checked him out and thought maybe sinus infection. She gave him antirobe (antibiotic) which he's taken for a month with no change at all.
I'm sure someone else will have great advice. The only thing that I can tell you is to always have a pocket full of tissues.