Out of all macros fats are the most fasting friendly so I think you should still get most of the benefits. With autophagy, it’s hard to tell as it’s not well researched, hard to measure, etc.
If you have to take it, then take it, do the best with what you have.
Btw. what disorder makes you take fish oil if you don’t mind me asking?
Most of the school of thought says that low carb things don’t break your fast. If you were wearing a continuous glucometer it would a barely show a blip if at all.
I wouldn’t worry about it. Mental health first.
I fast and I take an entire ramekin full of supplements 3x a day.