I think I’m somewhere in the last half of the Dark Night (honestly I don’t really know and I don’t really care anymore...I just want out of wherever I am!). Anyway I have practically zero concentration (I use a breath-counting strategy) regardless of the amount of intention/effort I apply. Obviously this significantly affects the quality of my formal insight/daily noting practice. Any recommendations for improving concentration (objects, techniques, etc) during these stages? Thanks!

Do you have access to the 3rd shamatha jhana? Sometimes hanging out there can give you some relief, which can then help give you the oomph necessary to keep going.

Is it possible you're trying too hard? To riff off of Andromeda's comment, if it were me I'd try a totally different approach. I'd relax. A lot. Take a walk, sit outside and watch something you enjoy, even if it's the wind blowing tree leaves. Then when you sit just keep that amount of effort going - use a very light touch without bearing down on an objective. I used to try way too hard when I was trying to get somewhere, and that caused a lot of unnecessary problems that seem a lot like what you're experiencing. The effort we put in trying to escape something like Dark Night symptoms can lean toward too frantic and over-the-top.

Andromeda...I wish I was that lucky! The closest I got was the first jhana on retreat last week. And that was extremely unstable.

and Chris...I think you’re right, especially if I’m on this side of ‘Equanimity’. 

Given that, and trying to balance effort and equanimity with what is, any recommendations on concentration objects/practices when the center of attention (breath at the nostrils) doesn’t seem to be working?

Chris offered some solid advice. I second what he says but I'll also offer what I found helpful.

When you're in dark night it's really difficult to concentrate. And that's ok. It's not the skill you should be developing anyways. In dark night you need to relax and let thoughts, emotions, and sensations to be there while not become entangled in the story lines. Shift attention away from thought in a relaxed fashion rather than in a gung ho kind of way. Deep breathing can help take the edge off a bit but don't try too hard to focus on the breath.

Meditation is a fine balance of relaxation, concentration, and contemplation of the 3Cs. Learning when to relax, when to concentrate, and when to contemplate is something you have to come to on your own. Practice as much as you can and experiment to find out the level of effort and relaxation that works for you. I personally only contemplate when the mind is sufficiently stable and there's sufficient curiosity to fuel the inquiry. You may also find that beneficial. A meditation journal will expedidite you through the process.

For dark night I found it helpful to review the re-observation and equanimity sections of MCTB regularly. Make sure to pay attention to the bits regarding acceptance. As you may have noticed, your mind is constantly in disagreement with how things are. Judgement and negativity. Self and otherwise. Getting entanbled in those thoughts can lead you on a marry-go-round chase taking you away from the here and now.

Acceptance is the way out but the breath can help soothe you through this process.

Chris and Ivory say lots of good stuff. Since 3rd jhana is out, I'll add this.

For me, when the late dukkha nanas hit especially hard there seem to be a lot of unpleasant sensations mostly in the abdomen/thorax/arms. It feels like my body is trying to die, and I can remember being really, really disturbed by this and spinning all sorts of unhelpful stories about what was going on. But now once I can tune into that it, there's a recognition--like "oh, my body-mind just wants to die again, it will be over soon" and then it gets easier to just observe rather than fight it.

Whereas trying to focus on the nose tip when this is going on might be out of the question, you may be able to pick up these sensations across a broader swath of body. And while they are unpleasant sensations, they are also kind of interesting and as you break them apart can feel almost like being painted with a paintbrush of pain with waves and ripples, kind of like water (at least this is how it is for me) and there are all sorts of interesting interference patterns created as the waves interact with the senstions of the breath. If you can cultivate a gentle curiosity toward the flow/impermanence aspect of the sensations that can be very helpful.

Edit: also, walking meditation. It was walking that first got me to high equanimity. LOTS of walking, fast walking through the city. And my most important insights have come from walking. For the dukkha nanas, looking for the interference patterns between the unpleasant bodily sensations and the sensations of walking (just as with the breath) can be very helpful.

Thank you all so much! It’s like you already know this stuff, but the lack of clarity and equanimity along with increased doubt keeps you from being able to stick with anything for very long.

On retreat last week I was able to sit with a broad awareness and watch the micro movements in the body, but unfortunately didn’t have enough equanimity to just be with that and instead tried to force something that wasn’t there. And I did do a lot more walking than usual  since it seemed to be the only practice that didn’t increase my level of frustration.

Here’s to hoping that your words will be the encouraging guidance that I need! Thanks again!