BluebirdSR20Dubai

I bought a Nissan Bluebird '97 with a SR20DET engine and AutoTrans (97 until now it has done 202K) a few months ago just to have a car to play with, like tune up and stuff. I noticed a few problems, first thing the car's auto gear change is REALLY violent from first to second, really shakes up everything inside the car, second, the car has flat lines, if I start with 0KPH the car hardly moves the RPM just goes up like I am acceralating very normally even tho my leg is welded to the floor, but if I accelerate from 40KPH/80KPH+ the car's RPM goes right down to 6500RPM, and feels like the car really has some grunt. One more thing, in the past my cars all had switchable Overdrive buttons, but I see a overdrive button infront of the gear which is just there, but I can't press it and it seems it has backlite, but I've never seen it working.

What could be the problems, I know the gear problems, but are those flatlines problems from the gear box or something else?