Do our legal provisions and processes allow Government to pronounce a uniformed service member guilty w/o trial & w/o evidence?

Gene, it appears many things are being mushed together that shouldn't be. Criminal law requires quilt beyond reasonable doubt. The "preponderance" aspect is found in civil law which is a lower standard to meet. Innocent until proven guilty isn't in the Constitution. Closest aspect would be the 14th Amendment which talks about equal protection under the law. When it comes to administrative procedures, that's where you find much of what goes on in the military. The two prior standards don't have to be met in administrative procedures. You also don't have 5th Amendment or double jeopardy protection in the administrative arena. If a duly appointed investigator is performing a JAGMAN and you refuse to answer questions, you can be punished for not answering. If one authority issues say a reprimand and a senior authority decides to bust you a rank, that's legal (although a morale killer and demonstration that the CoC isn't wired together well).

Even Courts-Martial are not the same as criminal courts although they share several process, rules of evidence, etc. stuff. Courts-Martial was established by Congress under Article 1 of the Constitution and Federal Courts under Article 3. They operate differently. Article 3, 5th Amendment RIGHT not to self incriminate, Article 1 PRIVILEGE not to self incriminate. You see Congress felt the 5th Amendment aspect should be conveyed to military members but couldn't grant a "right" under Article 1 (why? a lawyer is needed here because I don't remember). That's the extent of my engineering legal mind as I learned some of these differences when having to do JAGMANs, sit Court-Martials, etc. The worst thing you can do is make broad sweeping statements that somehow by saying them, makes it true.

Finally, if a member believes their DD-214 that gave them a DD, nasty RE Code, or whatever, the DD-214 is an administrative document in which an administrative appeal can be made to the governing Service's board. In the Navy, it's the Board of Correction of Naval Records. The other services have a similar board. These boards only look at if the process was conducted correctly, not necessarily the end result. The boards don't substitute themselves into the judgement arena either. A typical correction that a board will approve is an improper RE code (criminal act) when the reason the member was tossed was flunking the physical fitness test. A clear error. The correction that would be made would be to change the DD to honorable or other and the RE code to the one that talks about flunking the PFT. That's an unlikely extreme example but illustrates the point.

Preponderance of the Evidence doesn't apply in criminal cases. there has to be proof "beyond a reasonable doubt". the US Constitution, 7th Amendment, gives citizens the right to a speedy trial, the ability to confront their accuser(s).
if said service member was found guilty without a trial or evidence, then he should have a line of lawyers beating down his door to file appeals.

"The Constitution stipulates that all are innocent, until proven guilty," It actually does not stipulate, or state that. Remember that guilty only applies to a criminal charge. And even in a criminal proceeding, the court will find you "guilty" or "not guilty". No one is ever found innocent.

"...in a Court of Law, by the Preponderance of the Evidence." Again, guilty is only in a criminal context. Using Preponderance of the Evidence as the burden of proof is for civil matters only.

"Given this legal premise, does a Court of Law include a Board of Inquiry in the Armed Forces"
No.

"and; does the Preponderance of the Evidence include a presumption of regularity and; is there a six-year rule under Military Law? Kindly explain the fine line in Law and in Practice; legal professionals are encouraged to reveal the truth about Law."
I'm going to stop right here. This is kind of a messy question, and asking anyone to explain the "fine line in Law and in Practice" is something you can teach an entire class on, and not meant for a small comment section. Also, the specific context and facts relating to your overall question were not included, which makes it hard to provide a response. (Does someone have a Board of Inquiry pending? Has it concluded? Did the person have, or was denied counsel?)

Which leads me to my final suggestion. Make an appointment with an attorney to discuss the specific issue, with all of the facts, and ask for advice. Most attorneys offer a free consultation. Good luck