i bet it's your linkage... especially since it got bent. is the shifter hard to move around in between gears and in neutral or is it just hard to put into gear. i ask this because the linkage may be binding against the exhaust or heatshield. when the car is moving the motor will torque forward which changes the position of the linkage slightly.. which may explain why your shifter is difficult to move while at speed. also make sure that you're not overfilling your transmission.. . i have a feeling you're not checking the level correctly.