Dodge nitro 2007 overheating and don't know what to do! When I turn on the cold air it gives a burnt smell!

Hello Scotty!

Love your youtube videos! Okay Scotty so I have a 2007 Dodge Nitro. It is the sxt 2wd drive model. It has around ~148,000 miles on it. It started overheating one day when I was going back to school and the gauge was rising and I could see the water on the hood evaporate (it was raining that day). I went back home to see that the radiator cap was loose (my father did not close it right when he was adding coolant). a month later I drove it an hour out of town and back and the gauge rose to the red zone and I had to stop before my engine blow up, coolant spilled out of the radiator cap. it did not overheat from then. I took it to some mechanics to fix a check engine light as inspection was coming up. They charged me $850 for a repair they said it was a vacuum leak and apparently the fan rely was no good so they replaced the entire fan. I took it back and the car was overheating a good 10 minutes later. (also the check engine light came back on). If anyone is reading this do not go to Garner Auto specialist! they wanted to charge me another $2000 dollars to replace a module that apparently is responsible for the check engine light to come back on. Any way me and my father installed a new thermostat, water pump and flushed our coolant system. The Dodge Nitro usually over heats in 20 minutes while driving and more quickly during heavy traffic. Scotty what could cause the Nitro to overheat. It can't be the head gasket as no smoke comes out of the exhaust. Also when I turn on either the cold or warm air on the A/C it gives off a burnt smell to it and the A/C does not heat nor cool very well what could it be???

Scotty thank you for taking your time to reading my story! You are the best!