Torque Converter Problems?

Doesn't sound like a torque converter issue to me. Sounds like a fuel delivery problem, or maybe even something worse such as burned valves. When you adjusted the idle mixture screws how did you do it? The best way is to do it with the car in drive. Loading the engine down, such as what happens when you drop it in gear, changes the idle mixture requirements a little so the adjustment should always be done with the car fully warmed up and in drive. Loss of top end power and engine shakiness is also an indicator that it's an engine problem, not anything to do with the trans. With no load on the engine (when in neutral or park) any misfire is far less likely to cause shakiness. Loading the engine down makes those issues really show up.

Have you checked compression on the engine lately? Have you put a vacuum gauge on it to see how much idle vacuum it has and if the needle stays pretty still or jumps all around?