I just remembered, I also have a bag of goldfish food that my cat carried in through the window. Alas, due to the presence of said cat, I have no goldfish to feed it to. Compostable? (the fish food, not the cat.) :D
Kooky questions, I know, but hopefully someone will have a clue. I certainly don't. :/

I am sure that all three would be fine additions to the compost heap - but in the case of the sesame a very expensive one. Have you looked into what you could do with it in the kitchen? It's supposed to be very nutritious. Or offer it to a neighbour who would use it?

If the sesame powder is still good, you could turn it into tahini (which can be enjoyed as is in any number of ways, or included in hummus). But it should be fine in compost as well. The fish food should be just fine.

I would spread the powders throughout the compost pile and not just throw it in a big lump. Other than that, it will all turn into compost. The salt is not enough to worry about.

I'd apply it right to the soil / lawn / garden.
Things that are powdered are so easily gobbled by the compost/soil beasties that I like to have that happening in close proximity to the plants I'm growing. Flour or sesame powder would just sift down between blades of grass, or could be tucked under mulch, or could be turned in as you turn the soil for a spring garden. Of couse, it'd be fine in compost too - might give it a real boost of heat / fast action (depending on the composition you already have there).

I've been using all sorts of seeds and beans for soil amendment. I grind em up with coffee grinder, and apply as top dressing.