There's no problem, that's what it's supposed to do. It's called "Cool'n'Quiet". The CPU voltage and speed will vary depending on the load. That is to save power and make the system run quieter when it's not doing much.
It's good you set the RAM speed to the correct value, but you also have to set the timings and voltage like MadAdmiral mentioned.
The clock speed IS 3.2 GHz. 803.7 MHz times 4 is 3.2 GHz...
It's a BIOS setting (Cool n Quiet). The CPU is downclocked to save power and lower the temperature when it's not being used. I would leave it as it is. You don't need it running at 100% all the time. shortstuff beat me to that part.
Coolermaster Hyper 212 Plus. Beat by obsidian. It's $30 on Newegg.
Adding fans depends on the case you have. Personally, I'm not a fan of additional case fans. I once saw some testing done on the best way to cool a case, and I believe it was a very simple setup with few fans.
One thing I would definitely consider is adding dust filters to the fans, assuming they don't have any. It won't make the case any cooler, but it will keep it cleaner and allow you to not have to clean it out as much.