Very nice build. I have been doing something similar. Here is some advice from my experiences:
I use Gyokuto for a BIG damage boost to ninjutsu (+100) and thus shuriken/kunai. With Gyokuto, you throw less shuriken, but they hit much harder. Less time spent throwing is more time spent dodging. Use low stance for quicker standing dodges, less ki usage, and 10% more damage in low stance. It is more about mobility. Gyokuto also has a better living weapon attack form (lightning damage debuff for a good slow - works amazing with kusarigama's Reaper skill). It also charges just as fast as Aya-Komori and with Iga Jonin set, you regen the same amount of ninjutsu on LW use. I do the same thing you do, activate LW and cancel out of it to get the shuriken refund.
As for gear/build: I have two Medicine cases with +8 Ninjutsu Power and 4.x% Unlimited Ninjutsu(I don't use Yasakani Magatama). I do not have Unlimited Ninjutsu on all my gear, just chest and hands. My TOTAL Unlimited Ninjutsu is only at about 20%. My Ninjutsu power is 863. Shadowround talismans seem to have a similar effect compared to your build(I don't know what the percentage is).
I have the same as you for build capacity: 21 shuriken, 21 kunai, 4 fire shuriken, as well as 6 poison shuriken(for special situations). A BIG difference: I do not use Sloth, I instead use makibishi (I only have 8 equipped). That means that I can use them for bosses to slow them down, use a Living Weapon and recover more uses. I never run out of makibishi.
I just ran the same full no-shrine shuriken/kunai gauntlet of Demon King Revealed with Gyokuto. I never ran out of shuriken/kunai/makibishi.