Your Bump is set to 250 (highest value), also, if you increase the size of your original image map, then the JPG compression may create a less grainy bump.// or if you save them as PNG or tiff that may help since these are less compressed.
the bottom line here is that you’re trying to create a modelling effect using bump.
Bump is an effect created by using light and shadow based on the bump map.
You may get a better effect using displacement mapping, although your model definition needs to be high enough to create the effect.
Bump, makes the model’s surface appear bumpy. (but the model is still flat)
Displacement, will alter the shape of the physical model to create high and low areas. it deforms the mesh.
modelling the shape you want is always the best option (IMO)
although, on a Square bottle it’s trickier if you want that effect on the full length of the bottle, but it should be easy enough to do that with extrusion and some rotation of the mesh.
Quick rough modelling example.