My dog as a REALLY bad ear infection, stinky and all. Are there any tips to help brings that down? I feel so bad for him

What kind of infection? If it is caused or related to mites use garlic juice, or garlic oil. Mites absolutely HATE sulfur compounds and garlic has loads of it. But if it is a small dog you'd have to watch out for Heinz-body anemia. If it is a large dog don't even worry about it. Also, if using the medicine or ear drops your vet gives isn't working you can schedule an appointment and they will clean the ear out for you and that should clear it all up.

He really needs medical attention.

Call your vet back and tell them it hasn't cleared up Maybe they can prescribe some antibiotics

Avoid letting him hang his head out of the car window when on drives. I heard that when dogs hang their heads out of car windows it can cause a whole host of ear infections.

The first thing you need to do is call the original vet that checked him out back to tell them the treatment didn't work, and something more aggressive needs to be done. I'm sure he has more aggressive treatments available. Like any doctor, even a human's one, they want to go to the simple solution first before they order intensive tests, or more invasive treatments. Considering it's a pet, and pets can't tell you what's going on, how much pain they are in, and it's hard to calm them down or know what they are doing is an important thing, plus fear of being out of place and being touched by strangers, vet's often will do what may be most comfortable to the pet first. But if it's not working, go back. If still unsatisfied, get a second opinion. Just like you would do if you feel your doctor's treatment isn't working, or isn't correct. Perhaps time to try a veterinary hospital, not an office. Someplace like a human hospital, with x-rays, lots of waiting beds, nurses and doctors running about. They have them here in NJ, don't know what state you are in.