To understand these words, break them down. "Dis-" means to lose, or "loss of". So focus on the main parts...
Grace. Honor. Credit.
Grace has many meanings, but when used as "disgrace", it is referring to a quality of social/societal standing; it means:
3 a : a charming or attractive trait or characteristic (
source).
Honor too has many meanings, but when used with "dis-", it is referring to a code of conduct; not necessarily military, though this will often be the context.
Credit, in the same way, is not referring to your FICO score, but rather your credibility; some judgment on how believable you are.
Now, you can see these things have facets related to, or in common with each with each other, yet they are targeting distinctly different human traits. These attributes within one person may well affect each other, but they can be seen as different.
I would hesitate to call these even "near-synonyms". As post #2 so well illustrates, they are NOT interchangeable.