1. How you you configure Photoshop? The most obvious way is to set "Printer Manages Colours". However, I have recently discovered (others may have known this for longer), that in recent versions of Photoshop (CS5 or later), if you print like this and the image has an embedded profile, then Photoshop silently does a conversion to sRGB. This is not what you want. I discovered this reading a few recent threads on The Online Photographer. For the most detailed discussion see this thread:
http://theonlinephotographer.typepad.com/the_online_photographer/2015/10/photoshop-vs-printer-managed-color-printing.html
It's primarily about colour rather than B&W, but if you read the comments section there's a lot about the "Printer Manages Colours" issue.
There are several workarounds. One mentioned and debated in that thread is to set the printer profile to be the document profile, which I think was referred to as the null profile conversion method. Another is to print using Qimage, which allows you to set colour management off. I would add a third, which is to assign (not convert) the image to sRGB for printing purposes. This will "fool" Photoshop into not performing any profile conversions, and since ABW ignores the profile, this seems to work in my testing.
There is also a question of how to print the 21x4 in order to measure it and then create the ICC without stumbling into this problem. Same solutions, more or less, but with a couple of extra twists.
2. The ICC profiles that those QTR supplementary ICC creation programs create are intended to be "perceptually linear". Search this forum for a discussion, but note especially this post by Roy Harrington:
https://groups.yahoo.com/neo/groups/QuadtoneRIP/conversations/messages/12538
My summary of what this means is that the profiles result in a good screen-to-print match. However they do so at the cost of blocking up the shadows and losing shadow detail. Even Roy effectively concedes this point in that post. So if you convert to these profiles, watch out for lost shadow detail. You may need to edit to prevent this.
There is another way to use these profiles that prevents this. You can choose not to convert to the ICC, and instead just use it for soft-proofing using the "preserve numbers" soft-proofing setting. This will enable you to see how the image will print as-is without conversion and allow you to edit to get the print you want without loss of shadow detail. This is the standard piezography workflow, and I've written a blog post about it if you're interested.
3. Since this is the QTR forum, I should ask why you're printing with ABW and not QTR? There seems to be a general consensus that QTR will give you better prints, and will avoid the problem of Photoshop's silent sRGB conversions. However if you have a desktop, non-Pro printer, you'll have to deal with the issue of microbanding in the first and last inch.