transmission problems on 04 Ford Focus ZTS 2.3L

My son has a 04 Ford Focus ZTS 2.3L with 90000 miles on it that the transmission started going out two days after he bought it. We are trying to figure out for sure if it is something mechanical inside or electronic like a solenoid. The first symptoms were that the vehicle could go into first gear just fine then the RPMs get high so you have to hold back and then it finally switches into what we think is 3rd gear, but then never goes into overdrive. The overdrive off light would sometimes begin flashing.

The code that keeps returning is Shift Solenoid D stuck on. We have changed out the solenoid and even switched some of the solenoids around to see if symptoms changed to other gears and they did not. The car has been driven like this by my son for about 8 months cause no one can afford to fix it right now.

About two months ago the reverse began going out also. Sometimes the reverse works but when it does the entire car shutters. The part that is confusing me is that last night my son called me and said that he needed me to come and pick him up cause his car seemed like it didn't have any power. My husband went with me and I drove my son’s car home and discovered that it now feels like it was not engaging in 3rd gear now. While driving it I decided to try turning the overdrive off and see what happens and when I did it shifted into 3rd again. This is really weird cause it seems like if this problem is mechanical like a gear band that turning off the overdrive would not have changed the fact that it wouldn’t shift into 3rd. I have tried this before with the 1st to 2nd and turning off the overdrive doesn’t help that. Sorry this is so long, but if someone can give some advice I would really appreciate it.