Yes, you can use fish oil for SLD. If you want to make that part of your SLD oil, then you shouldn't take them right after a meal. You should observe the 1 hour on either side. You could take them with your ELOO if you wanted. Four caps is a small quantity per SLD standards, though. Depending on how much you want to lose.
As for the repeat...it's probably okay. Nobody really knows how much a flavorful burp or a good noseful of fragrance is worth, so the working plan is to try to avoid such things, but not get too wadded up when they happen.
I take a tablespoon of salmon oil. Currently, I make it part of my SLD regimen. But I've also taken it with meals, not as part of SLD, for the benefits.
Welcome to the forums. I didn't know there was such a thing as prescription fish oil! What was it prescribed for, if you don't mind saying?