Should I go to IG for HIPAA Violation by my 1SG and PSG?

Stop your sniveling! If you have four profiles then your condition is already a public record. Your 1SG and PSG didn't violate HIPAA by overhearing a phone conversation. They didn't take confidential medical information and share it with an unauthorized person. Why was the person on the other end of your call talking so loud that your PSG could hear it? Did you have the call on speaker? If you did then you gave up any expectation of privacy. Back when I was in as a leader I was expected to know everything about my troops. Privacy is one of the things you give up in the military. Leaders need to know what is going on with their subordinates unlike in the civilian world, secrets can get people killed in the military.

My advice. Do not sweat it and do not let them get under your skin. A med board gets reported to the pentagon as an undeployable. As such the entire chain of command has to report to someone higher about your condition and how it is being resolved. Your slot is going to be needed to be filled so they will want to know when this can happen.
So about knowledge of your conditions. You do know that the VA reports back to your medical officer and this filters down to your commander and 1SG? Your commander recommended you for a med board off the advice of the medical officer so it would seem normal that he would want to keep track of your progress.
Not knowing anything about your commander, or your chain of concern, keep in mind an administrative discharge can null out a med board. So fly straight keep your bearing and do not let them get under your skin. Some think that they can save the government money by forcing you out with a less than honorable discharge. Just a caution like i said i know nothing of the unit.

Private, first of all HIPAA covers medical personnel only and the holders of your medical records. While "Top" can be criticized for lack of good leadership principles he cannot, in my personal opinion, be held to answer regarding HIPAA nor can your PSGT. Your goal is to medically retire from the Army so don't rock the boat to do so will cause it to capsize and sink.

Your First Sgt should be made aware of all medical conditions that can effect your ability to perform your duties. By attempting to hide any of those conditions makes is very questionable for those proper decisions to be made. The possibility of placing you in harms way or those with whom you work with can place other individuals at undue risk. As far as harassment and intimidation? Some supervisors may not be the best communicators. I am not sure that is up to the IG to handle. Perhaps your First Sgt's Commanding Officer should be brought into the conversation. It is called, the Chain Of Command. That should work better for you rather than going over an individuals heads and blind siding them with a situation that should be handled at a lower level.

You might be able to go because you were “cussed out & intimidated” but hopefully you have proof & a witness, otherwise it’s your word against his. But as far as HIPAA, I don’t think there’s a case but you can always ask if there was. I say that because it’s right to think the caller figured it was okay since you knew what the hearing was for & anyone sitting in was your representative.

The vague narrative presented is insufficient to render judgement, on the surface it sounds like an effort to maximize benefits to me. It would also seem that the Young soldier is is not particularly valued by his unit and is a particularly nasty divorce in progress.

who is starting and injecting these questions into military minds??? STOP

Thin line between your HIPAA rights as a citizen and your HIPAA rights as a soldier. HIPAA laws were created to to protect your medical information from being shared with those you have not given permission to view it. And that permission must be in writing, by name. Your rights as a serving member of the military are codified under DoDM 6025.18.
https://www.esd.whs.mil/Portals/54/Documents/DD/issuances/dodi/602518p.pdf

There are indeed circumstances where the military command can supercede your HIPAA protection rights. You need to verify if that process was in fact implemented, and then decide from there how to proceed.

Go to chaplin and/or patient advocate. Before an IG will get involved you have to take it to someone who can step in and you need to ask for a transfer. Maybe, find the number for the med-hold unit; if there is one...

First off before you even attempt to make the complaint make sure that you have your ducks, chickens pens and pencils lined up because once you make this complaint theres no turning back. It is a SERIOUS violation to mess with HIPPA and make claims that some has violated the use. If everything is in order and you have talked to the people that you need to talk and if they say gtg then have at it. I recommend not to make a complaint unless there is truth behind it and evidance. Not cause you don't like what this person did or say. Between UCMJ and State and Federal laws about HIPPA just you making the assumption that a person may possible violated something with go out in the world very fast. Talk to the people you need to talk to first. What we may think is a Hippa violation may not be one.