You have a steering cable with a rack and pinion helm station. Very likely all shot.
Looks to me like you have all kinds of work to do.
Is the motor locked up?
Yes, mechanical. You have a steering cable that is most likely froze up. Remove this nut and bolt and see if your motor turns without the cable hooked up. If it doesn't turn you probably have more than one problem.
Not sure if this was said before but try to borrow another compression tester and see if it's different otherwise yes it could just be wore out.
Unless you have a dyno or a big test tank you can't re-creat that.
I'm assuming you looked at this......
https://www.marineengine.com/parts/johnson-evinrude-accessories/index.php?year=1983&model=Power+Tilt%2FTrim+1983§ion=Power+Tilt+Kit+25-35+Electric&yid=34152&mid=34157&sid=37038
Grease doesn't go into the tube....it goes around the outside of the tube and around the bushing.
They do make upgrades, a stainless tube and a nut with a grease fitting in it so you can periodically grease inside the tube.
Replace it.
As to why it fried.....I wouldn't know.
I looked up your part and it's pretty pricy so you may want to do more testing of the other components.
I know less about that.
Here is a video of the simple test of a 3 wire rectifier. Remember a rectifier just changes ac energy from the stator to DC current.
This is just testing the diodes but it usually shows the signs of a bad one. There are more complex tests online but watching this simple test gets your feet wet...