Science of Cooking

In my area, cooking wine does not exist. I can only easily find Sherry (for drinking) at 15% alcohol. I was told it should have 20% to be shelf-stable for ~6—24 months.

There is white port at 19½% alc. Not sure if that differs much from sherry in taste, but I suppose 19½% is close enough for shelf-stability.

Should I add table salt to the sherry to make it shelf stable? Or add brandy? Or switch to white port? Or even just brandy?

My main use: less than ~½—¾ shot mixed with corn starch as the thickening basis for stir-fries. I don’t really use sherry for anything else. I don’t even drink it because I so commonly use it in stir-fries that as a straight drink it’s like drinking Kung Pao Chicken because I can’t mentally dissociate it.

I also wonder if I should be looking for dry sherry, or simple sherry. I want the stir-fries to have the sweetness of strong sherry, so I guess dry variants would be contrary to that.