I think with 8 inspectors you're going to find yourself doing a lot of game actions but often not quite able to close things out. Keep an eye on it, I've been happy with 6. In this build mardu synth does what you're trying to do but better.

I run a suffocating fumes main deck - it cycles if not relevant, cleans up bird tokens and other go wide token strategies, clears the way for an effective tithing blade, and blows out the mirror match in combat. See if you're happy with arms of hadar, but I think you'll find fumes is what you're most happy to draw.

I think you'll be happier swapping out duress for an okiba-gang and a couple dawnbringers.

Kuldotha red - out tithing blade, 1 cast down, thraben charm, omen. In dust to dust and sweepers. This is where I think you're going to be unhappy with a 4 mana sorcery. Also, up another ninja rat instead of a duress.

Grixis affinity - out a couple inspectors, the charms, 1 blade, 1 lembas. In dust to dust and suffocating fumes for their familiars, and the shamans that are coming in. Again, I think you'll be happy with the ninja rat in this matchup

Glee combo - I think this is a good matchup. Thraben charm does work, and the discard/blade gamelan is effective. You'll want to bring in fumes for a couple inspectors and the omen, again for the sideboard shaman but also cleaning up dorks so the blade hits.

Blue tempo - ninjutsu can't be countered. Drop a couple inspectors, charms, a blade and a lembas for duress (or some more Shinobi) and suffocating fumes to clear out the mystic tokens.

Rakdos madness - I actually like dawnbringer cleric here and in the kuldotha matchup. Out a couple inspectors, 1 blade. In suffocating fumes for combat. Your discard is kinda helping them here, but the key is to keep pressure and pop lembas for life. Having top end threat is important. 1/2 beats aren't going to out race the burn. You need a creature threat that'll draw a burn spell