Dan,
I don't think this is the correct place to discuss SPN/SPD or RE codes since they do not concern the VA in a -official- capacity. Though, I've heard stories about them having an impact in some VISN's. If you have questions on SPN/SPD codes your best place to start looking for answers is at www.veterancourtcodes.com That site is dedicated to the kinds of issues that you are asking about.
As for the advice I personally have for you.....
You are very angry. That is understandable. But this happened over 33 years ago. You would be wise to let go of the injustice of the -past-, such that you can focus on the injustice of the present.
The SPD code KDB is for a "Hardship" discharge. There is nothing negative there. It is the correct code for a hardship discharge.
The RE-Code 4E indicates a non-waiverable bar to reenlistment this is typically given for medical reasons. Frankly, after 33 years, and given your stated medical condition, I don't think you are going to try to reenlist so again, nothing negative there.
Neither separation code merits "Better" treatment. But they don't indicate that you should get worse treatment either. I've known horror cases relating to SPD/SPN codes. This isn't one of them.
The Reenlistment Code RE-4E is a blessing in disguise. You can use that to document in service diagnosis of your injury for the purposes of service connection.