Good answer Phil. There appears to be agreement that the KD base gravy is a good one but the approval of her dish recipes is not quite as solid. I guess a personal choice needs to be made as to whether to proceed down the individual spice route or use blended powders. I see a use for both in different situations.
You raise a point that did my head in when I first started this "hobby". To my mind the inclusion of a "curry powder" as an ingredient to make "curry powder" was just so utterly confusing. It made no sense to me at all. Why not just give the ratio formula of the individual spices to go into the final powder and make it? It's like using a word in the definition of that same word. I struggled to understand it but eventually realised that it just didn't really matter. I had to ignore my inner brain squirming around in discomfort and accept that this is just the way BIR is done. It's the end result that matters. The food on the plate.
I regularly research and experiment with masala blends, mixed powders and pastes. I've recently found 2 different formula for Madras Curry Powder that I will try out very soon. One in particular.
https://www.youtube.com/watch?v=24CfBr5t1Fs It is claimed by the presenter to be identical to the brand commonly found in "the green can", This could be one of at least 5 different labels packaged in green cans being, Ship, Camel, Indian Classic, Kitchen Xpress or Mother's Recipe. Probably Mother's Recipe but the mystery has me hooked. I've tried some proprietary masalas that are terrible and others that are amazingly good.
To put the discussion back on topic, I read this thread from late 2005 to early 2008 on the KD Base Gravy.
http://www.curry-recipes.co.uk/curry/index.php?topic=579.0. I can see that you have tweaked her recipe only very slightly Phil. I'm puzzled by reply number 8, page 1, where out of nowhere comes the question of how long you can keep spice oil. There is no prior mention of reclaiming spice oil from this base gravy.
This short 1 page thread from 2006 gives a chefs opinion (Spanish Indian Restaurant) of the ingredient ratios in the KD base. It is quickly derailed though into a discussion about Lemon Juice in CTM and Mustard seeds in Madras.
http://www.curry-recipes.co.uk/curry/index.php?topic=695.0. The key points made by the chef was not enough tomato and no seasoning as in Garam Masala. Once you start adding more onion, as he also suggested, you just get into a larger quantity overall which the OP has covered.