Running rich, rough idle and stalls when driving?

Hello, I have the vehicle listed above Laredo. I purchased it a little over a week ago knowing there was a problem with the fuel system. I started by checking the spark plugs because the previous owner told me he just changed them. They were auto light and carbon found, and he had only replaced five the other three were Bosch and I think one may have been original. The vehicle has 187,000 miles on it but is in really good shape cosmetic wise and I believe it had been pulled behind a motorhome. I replaced all of the spark plugs with Bosch platinum and I have also replaced the throttle position sensor in the coil on plug packs. It has a rough idle, it is running rich, and I can smell gas while it's running. I believe there is an exhaust leak somewhere behind the engine as well. I also replaced a bad thermostat. It also has a knock or tapping sound, but I believe that to be the camshaft as it comes from the center of the engine. When I try to drive it, it will stall several times but when in park and above 1,500 RPMs it seems to smooth out and run well. Thank you for any advice.