No way you will be nodding while you are tapering. If anything, you'll be mildly dope sick and uncomfortable the whole time. Only way you can catch nods AFTER decreasing your dose is either by changing the way you take them or lowering your tolerance. There are a few ways you can get drugs into your system with varied amount of effectiveness. Injecting will result in more of the drug entering your brain compared to eating because it doesn't go in the stomach where some is destroyed and then have to pass through the liver where more is removed. So, 45mg injected will be far more effective than 45mg eaten. Smoking and snorting will be somewhere in the middle, as a fair amount is lost in these methods compared to IV, but probably less than eaten.
The only other way to increase the effectiveness of a drug is to lower tolerance, which in this case would mean he'd have to had taken less than 45mg/day for a time, or started taking 45mg all at once instead of spacing it out through the day. It'd be pretty easy to tell if he is taking it all at once vs spacing it out(visually see, ask about habits, or if he is nodding out more than one "episode"). Also if he stopped taking it completely for long enough to have his tolerance drop, it'd be pretty obvious as he'd be terribly dope sick in a way that couldn't really be hidden.
I can't say conclusively, but based on the information provided I'd be surprised if he hadn't relapsed. To be honest, if he is still buying drugs off the street then that is a major part of the problem. That's a bit like trusting a child to only buy 1 piece of candy when it has enough for 20 and no supervision. Idk what personal experience you have with addiction, but the disease incentives people to lie and cover up their drug use. By lying, they get the neurochemical reward of the drug; by telling the truth they get the neurochemical punishment of withdrawal.
In my opinion, you should leave him if he isn't willing to get help. Apart from the dishonesty, addiction will cause you all kinds of problems if it is left unaddressed, and it is not your problem to address. You can support him but you can't do it for him.