My 2000 Jeep Grand Cherokee keeps overheating...complicated...Help!?

When we got the Jeep last October, my husband had to put new brakes on, calipers and all. While he was bleeding the brakes, he was doing something else when bam, the radiator blew. The fan wasn't working. So, him being a pretty good home mechanic, he put on a new fan and radiator. He also went ahead and put on a new coolant sensor. The rest of the system looked good so we thought the problem was solved. A few days later, I had outpatient surgery and my best friend was driving me home. We went through a drive thru on the way home and we were sitting there when she asks me why the car was smoking. I had her pull it over into a parking spot immediately and popped the hood. The thing had overheated! A guardian angel stopped and let me know the fan wasn't working so just let it cool, replenished coolant, and it should be fine to get it home, an hour away. So turns out the fan wasn't kicking on. We were trying to figure out how to fix the relay but in the meantime we just rigged the fan to the battery with a toggle inside to flip on when sitting. But now, it starts getting hot really fast and flipping the fan on makes no difference. It hasn't overheated but gets super close and too fast to risk driving in heavy traffic on hot days. The motor only has 33K on it, total of 162K total. 6 cyl. The newest thing is now the air conditioner starts blowing hot air when I bring the Jeep to a stop, cold when moving. We had it checked by mechanic before buying + passed! Help!