Anybody have recipes to share beyond the basic ratio on the can?

I saw one recipe that said you can tone down the heat if needed by adding 1/8 teaspoon of salid oil (no brand mentioned) to the 1/4 cup of powder and 1/4 cup of water. So reduce the amount of oil accordingly for the smaller batches. I personally never need that large a batch, so I'd say just add to taste and experiment with some of the other suggestions and have fun with it. They also indicated to use cold water and to let it sit for at least an hour before using. I always had requested the house (powder) hot mustard in restaurants over the prepackaged and I'm glad this is available to make my own.

For seller: if i order a can today, what is the expiration date on the can?

On the bottom of cans is the date stamp I own two both have the same date stame 1 5.2023 x 2 cans bought 1 year ago.

What is the shelf life of the can after opening for the first time?

The only date that I see stamped on can is 2017. 9.25 So I am thinking this may be the shelf life but I am not sure. It is in powdered form so I mix 2tsp of product with 3 tsp of water. It is the best!

what is the best way to store this for freshness refrigerator or freezer?

I've found with both mustard powder and wasabi powder, it's best to refrigerate or freeze once it's been opened. I have kept some for a couple of years that did not lose their heat. I'm Japanese and I find this to be the best hot mustard powder!