What exactly do you mean when you say it wount go past 3500 RPM's. Does it shift at that point all the time, not letting the engine rev to 6K? Or is your engine not able to go past 3500 RPM's even when the car is in park or neutral? Symptons such as that suggest your MAF sensor is bad. However being you can't get reverse suggests your transmission is gone. If the controller was bad, you'd get a CEL. The tranny controller is in with the ECU.
You may very well have 2 things going on here.
As the 4th gen ages, its owners get younger.