You don't need vinegar (although some recipes call for it). A dry white wine will provide all the acidity you need. You control the acidity by the amount of reduction of the wine. To get very controlled acidity, reduce almost to dry and then add a spoon-full of water so that your butter can emulsify. My classic proportions are (metric but can be transposed ...
One time I made a mistake making fish stock. I put it on and fell asleep thinking it would be a short nap. Some hours later I woke to find the stock simmering. All the bones and heads were GONE. This is not even a hard boil!
I believe everyone who says fish bones can soften with pressure cooking. Think: When has a fish ever had to live in boiling water? ...
The vacuum-packed-ness of vacuum-packed foods can help keep food fresh by reducing oxidation, but it doesn’t have any effect on safety. If it were originally vacuum-packed but then gas developed from putrefaction then that would be a bigger concern... but there would be absolutely no question whether that was the case once you smelled it.
Is it safe to store fresh meat and fish for a bit longer at 33F than at higher temperatures? Probably. OP's original question asked about two weeks, and the answer is: at 33F, food is probably safe for greater than two weeks, per the scientific literature on food safety. I know everyone wants to quote FDA regulations or whatever here, but they are a one-...
try vacuum sealing the meat of fish before storing them either in the fride or freezer, removing air will allow you to get longer preservation in the fridge
(due to lower umidity and oxidation rate)and better quality when you freeze the product avoiding freezer burns and big ice crystal formation
Storing food in this manner would not be a good idea.
An ice water bath as you describe will prevent the food from freezing, keeping it barely above freezing temperature.
This will not allow uncooked or unpreserved meat or fish to last any longer than the usual recommendation.