I have seen this in the past before. I was taking a mix style called Isshin Shorin Go Ryu (Isshin Ryu, Shorin Ryu, and Goju Ryu Karate).
We had two Shodan, a 1st Kyu, and myself all doing this art and learning Jujitsu from one of the above Shodan.
The instructor found out and gave the Shodan the boot for teaching us Jujitsu. He told us we were not allowed to learn from both and we had to choose. He told us we could only serve one master.
The Jujitsu instructor said that he did not care what we did either way and that we could continue training at both, or with him only.
We all continued studying Jujitsu. I quit the Karate class because I did not want to disrespect him and I found him to be too arrogant and putting himself in the place of my only Master (God). The 1st Kyu stayed until he finished Shodan and then he told the truth, and got the boot. The Last Shodan continued to study and got his Nidan and then told the truth and got the boot.
The instructor gave them their promotions and certificates and said they were not allowed to use it as a reference for teaching. However, he was kind enough to get them promoted in Isshin Ryu Karate from another foundation and he had no say over that reference. So even though he refused them to use his own personal art, he did hook them up with something useful.
In my opinion, it would be easier for you to find an organization to test you. Here is a link to the PCMA
This is a good organization and they are fair. They understand things like this happen and they are there to support. They would not give it to you, and they would expect you to test for Shodan in person, but all of the board members have been doing MA forever, to include Lunsford Sensei who is an Advisor of the Aikido portion and holds 6th Dan. You also have Soke Hummerstone that is the head of Aiki Tora Ryu Aikido.
Each specific art is lined with general requirements. A person can add to, but not take away from in most cases.
Anyways, good luck Derek and I hope everything works out for you. Keep searching for support, someone will take you in and support you.