2002 Dodge Durango RPM seems to run high

02 Durango / 4.7 lit-2wl dr. Vehicle idles @ 750 RPM constant w/ A/C on-(No problem with idle) When driving 40 mph, tach shows 1400rpm and it never seems to slow down when you let off accelerator--it just keeps rolling at same speed, making it very difficult on brakes because it seems to take quite alot of braking to slow vehicle-especially to STOP. I can feel torque converter bump a couple of times just before a complete stop, as if it is compensating for higher than normal rpm. Also, while driving 55 mph or more, when you completely decelerate, the tach increases a bit -then drops to 1000 or so, then increases again until it finds a comfort zone, then remains constant, ie: you feel vehicle surge a bit then slow down, pick up mph, then constant. Replaced TPS-Mopar OEM, checked vacuum lines (visably). I'll need new brakes real soon if not fixed-this thing just does not slow itself down! Sure would appreciate your expert advice. Thanks!