This is a common problem for effects like this that are highly directional. This is why a lot of effects like this tend to be radial and symmetrical with the directionality built into the particle system. Unfortunately there isn’t a perfect solution for this. You can help the issue with zooming out as you mentioned. Usually you need to counter this zoom by scaling the sprite in the engine so it doesn’t look weird. You can also use non-square frames to help minimize empty space in the texture. If your texture is greyscale, look into packing the frames into the rgba channels to maximize texel density in each frame.
If you have the budget, alembic or VATs might be another option. This would create physical geometry instead of baking it into a flipbook.