Your situation sounds frustrating. I hope you can get good guidance with the divorce proceedings. I posted earlier about a hair follicle test. My son is hospitalized after an overdose. One of the addiction Drs suggested we get a hair follicle test because it would show a lot about his drug use. I don't know if there are different varieties of this test? We were told it could go back almost a year, show type of drugs and also pointed to severity of use during certain time frames. My daughter in law had to authorize the testing because our son was under sedation at the time.
One comment the Dr made was that the tests are effective and there is a myth shampoos will erase signs of drugs but he said no. But if your husband kept delaying the test, my guess would be he wanted to have as much time pass as possible when he was not using. I had never heard of this test. Good for you asking for one, very wise.