It appears from what you have posted that my information was indeed correct - Mississippi does not allow write ins, and it is past the independent filing date.
In order to continue his candidacy, McDaniel must win in court - which is a whole ‘nother kettle of fish.
It seems there are various remedies that could be granted if and when he wins his case:
Re-run the fraudulent run off
Allow an Independent run My McDaniel
Allow a write in ballot.
But all require a court ruling based on McDaniel’s claim of election fraud.
Your information regarding state law is irrelevant.
US Senator is a federal office and thus is subject to federal laws.
Mississippi’s election laws in relation to federal offices don’t matter and they know it. Federal case law is solidly against them in this case.