Use distilled white vinegar instead of white wine vinegar when making the own dressing for gifts

Vinegar, in general, has distinct acidic characteristics that will affect a recipe; it's often used for this reason. For instance, in marinades, the acid is used to break down muscle fiber and help flavor penetrate. In Cevice, the acid component is used to "cook" the fish.

Additionally, the different types of vinegar have different flavor characteristics. I, personally, don't much like red wine vinegar as I find it kind of bland. I much prefer balsamic or champagne. So the question you really need to ask yourself is, "will the flavor of the red wine over the white wine adversely affect my dish?" You might ask the same question about the garlic.

So subbing one type of vinegar for another is fine if you're looking to replace the role of the acid in a recipe (also why you can sub lemon juice). Whether or not you feel the flavor can be substituted is really just a matter of personal preference. If you don't know ahead of time about the flavor, try it and find out for sure.

To specifically answer the flavor characteristic for your question, I'd say yes. Red wine is OK. As pointed out, swordfish is a hearty fish and should hold up fine. I probably wouldn't sub balsamic, would use champagne as a priority, would think long and hard about apple cider. If it was a lighter fish, I'd be much more wary about red wine.

There is not really a turning point. The way that wine goes bad is the process of making vinegar. From wikipedia:

The word "vinegar" derives from the Old French vin aigre, meaning "sour wine".

The Canadian government limits things that can be sold as 'vinegar' to something with an acetic acid content of 4-12%, so you could do the technical-bureaucratic thing and wait for the acetic acid to get up to 4%.

If you aren't hung up on technicalities, then you can use it as soon as it gets sour enough. It is done when all the alcohol has been changed to acetic acid, but it is a bit hard to taste since the acetic flavor dominates.