I thought I might share something of my own experience. Please let me know if you have any questions about this. I read this thread before bed last night and it stayed with me; I wish you all the best and I hope that my own suffering may provide some benefit for you.
I was addicted to benzos for probably 5-6 years, started on xanax and then went to diazepam. Dosage skyrocketed for me, very quickly for a few reasons I will examine. In comparison, I was not on huge doses, but I was taking between 100-150mg of diazepam a day. At this stage, I begun experiencing breakthrough/tolerance withdrawal and this never left me. I also began using opiates (codeine, then morphine, then heroin and finally all that maintenance stuff like methadone and suboxone) to combat some of the withdrawal.
At this point, I should mention that I have epilepsy. I had it pretty seriously as a child and was prescribed multiple anticonvulsants, mainly GABAergics. It seems likely that this was what caused my extreme benzo withdrawal syndrome. For me, the withdrawal from benzo's, even when tapering very slowly, was incredibly harsh- I had intense seizures (which I can rarely have anyway) as well as hourly absence seizures (ranging from fluttering eyelids to complete automatism). I hallucinated, I experienced psychosis, I was blacking out, I was diagnosed with everything from PTSD, bipolar to dissociative identity disorder (this after I revealed that I was sexually abused as a child). Truth was that my CNS was kindled from my childhood on GABAergics. Of course, I did not know this would happen and neither did the medical fraternity either apparently.

No surpise, doctors rarely know shit about the truth of benzo's. Anyway, I manged to get off them via my glacially slow taper, and eventually went to a month long detox/rehab to get off opiates. I also ingested ayahuasca after this point as a way of healing my psyche and it fucking saved me. I don't neccesarily recommend that, but hey, just thought 'd mention.
Anyway, I stopped taking benzo's completely in 2011. I did not consume any for several years; in 2014 (I think) I got complacent and started to take stuff like diazepam, etizolam on the odd occasion. The effects were strong, so it appeared my brain had recovered, but the effects were no longer all that pleasurable- just a kind of dull tiredness, and after about 2 days I could be eating empty capsules for all the good it subjectively did. I avoided dependance; in fact, did not even contemplate it. At one stage, my girlfriend got some etizolam and I binged on it and diazeam for about two weeks and experienced very strong rebound withdrawal from this. It only lasted for 3-4 days, and was comparatively mild, but it told me that my brain had not, and is likely not going to, recover from both early childhood on GABAergics and then a large proportion of my twenties on them. The only GABAergic that I can take and not feel afraid of is GHB, and only occasionally. Alcohol gives me intense depression and anxiety the next day, even if I only have a glass of wine or a beer. I do not cope well with stress; I tend to almost dissociate and the world appears to be distant, unreal.
I guess I am trying to say that playing with benzo's, on and off, is really destructive and dangerous. These are simply not drugs that I think human body can tolerate; they effect something so vital and primary in our nervous system and I do not think we have evolved any ability to actually tolerate this. I really think that benzo's will become the 21st century barbiturate or chloral hydrate; sledgehammer solutions that are extremely brutal and primitive and dangerous. If you have been addicted to benzos, do not kid yourself into thinking that you can use them consequence free- I am afraid that this is not possible for you
or me. I would also urge you to rethink resuming heroin use. It is tempting, and I agree that benzo addiction is much, much worse, but heroin will not actually help the benzo withdrawal- in my experience, opiates can make it worse by adding nausea and that dopaminergic anxiety/irritability to the mix. Sure, you are physically relatively comfortable, but the crazy thoughts don't stop and quitting benzos and opiates simultaenously is incredibly painful (though, in the full throes of benzo withdrawal, I could barely feel opiate withdrawal).
Its up to you. You are responsible for what you put in your body. Addiction makes that seem untrue, you can feel automated and robotic- every fibre of your belief is saying I will not use even while your body appears to simply override this and do what it want. The human brain is remarkably adept at out-sourcing and automating tasks that require very little thought or investment, and unfortunately, it does this incredibly effectively with addictive drugs. You need to try and stay firm, or totally outsource responsibility for your dosing- I ended up collecting my diazepam from a pharamacist that also dispensed my methadone, so I couldn't take more than I was meant to. I simply could not do it myself, I had to create a situation where I was forced to do so.
Bit tl;dr but I wanted to share my experience in the hope that you might gain something from this. All your to-ing and fro-ing is not useful to you. It is the addiction that is making you think it wise to "test" how dependant you are- you don't need to test for that, you took the benzo's using that as a reason- the point has been amply demonstrated. I really think that a supervised taper will be effective for you; it was absolutely successful for me, I was able to emerge from my psychosis. I have completed university studies and am working in a really satisfying job as a result. I truly thought my life was over. Its by no means smooth sailing, I experience depression and anxiety and very regular suicidal thoughts, and I cannot say that I am overjoyed at my life- but, hey, its not completely defined by pain anymore and that's gotta mean something.