If the whole purpose of this brew is to showcase Belma, then I would say a pale, dry APA/IPA hybrid would be better choice.
Strive for that high level of drinkability in terms of manageable abv content, smooth hop bitterness, high hop aroma, and low residual sweetness, and no toasty or roastiness.
Mash low to aid dryness and boost hop character. Go with a clean yeast (plus starter) and a clean grist. A very simple grain bill. Nix the dark candy sugar. You aren't making a Belgian Dubbel here. Use sucrose or dextrose instead.
Otherwise... if you're set on the Black IIPA, it seems like too much oats are being used at 10% of the grist. I would personally go with wheat malt over oats for head retention in an IPA, but that's just me. Secondly, you have a lot of the darker SRM malts, half of which you probably need. I would look into simplifying that part of the grain bill a little bit more.
Mash hopping, FWH'ing, and Bittering is overkill. Go with a simple bitter. Belma is not high on the cohumulone level so it should provide smooth bittering if used in reasonable quantities. I would shoot for 30-40 IBUs with the first addition, a small mid charge addition at 30 to boost the IBUs, and then pound it late at 15/8/0 for that flavor/aroma to shine through... with much, much more hops than what you have here. The dryhop should also be more like 7 oz. for a 10 gallon batch. 4 oz. will be quite weak.
The last and most important thing I see with this recipe is your water treatment additions (7g baking soda / 6g chalk / 2g epsom salts). Those choices & amounts will most likely ruin your beer. Do you have a water report which suggest those are the proper things to add for this style of beer? You will most likely add a lot of unwanted alkalinity and sodium. I would do some more research and, if needed, use Gypsum + Calcium Chloride instead (in the proper amounts).