I have a few TH 75's and a TH 60. They do not like to be run rich. Tuned correctly, they run like clockwork.

I am afraid that you are too far off and it is time to start over.
http://www.towerhobbies.com/products...owg0175mnl.pdf

Pull the carburator off and adjust the low end needle per Tower's instruction by looking up through the throat from the engine side. There you will see the mixture needle and spray bar. Adjust these per the instructions. Don't leave a gap though, Tower has posted on their webpage that there is no gap.

Another good trick is to pull the carb and hook up a clean fuel line to the fuel inlet. Fully close the idle needle screw  by turning it clockwise until it stops. Now slowly open the needle screw while blowing air into the fule line with your mouth. As soon as air starts to pass through, stop. This is a good starting point.  Reassemble the carburator onto the engine. Start with the high speed needle at  2 turns out. Fuel up and make sure you are not flooded before starting up. Your needles are set very rich and the engine should start quickly.

Set the high end needle first. Turn it a few clicks at a time listening for the engine to gain rpm. When you think you are close, pinch the fuel line. If it dies quickly you are too lean, richen a little and try again. If it picks up rpm you are too rich, lean it a few clicks and try again. When you have this set shut off the engine and let it cool. If you have a tach, use it. They make tuning much easier since you can watch the numbers climb or drop.

Start it up again and run it up to warm it up some. Lower the throttle and let it idle for a full minute. If it slows down and dies then lean out the idle screw 1/8 turn. You can also pinch the fuel line at idle. It will take longer for the engine to be affected, but you will tell if you are rich. Keep leaning the low end until it maintains idle for a minute or more. Now run it up and drop it back to idle. Let it idle for a few seconds and then go wide open. The engine will stumble if too lean. Richen it up a little and try again.

Now have someone hold your plane pointed up at full throttle. The engine should not slow down or die. It is ok if it speeds up, a little. If it dies or slows down richen the high speed needle three clicks and try again.

You should be set to fly. Remember that the low end only needs to be turned in 1/8 turn increments or less. Once the low end is set you should not have to change it again unless you change nitro blends. Even then it will only be a small adjustment.  Those are the basics of glow engine tuning.