This is why I always speak out against progressive fork springs. They are a "one size fits all" spring. Sure, the progressive nature of the spring accommodates a much wider range of weights than a single rate spring would, but that does not mean that the spring will work well for you. In your case, you could be using a fork oil that is too thin, but based on the intensity of the bounciness it is more likely that your fork springs are simply too weak for the weight of you and the bike.
There are plenty of online calculators (racetech, sonicsprings) that can help you to determine the correct spring rate for your weight so that you don't have to depend on springs made for a broad weight range.
The oil level won't affect the bounciness much; it only determines the air gap in the fork, which will only help you fine tune the suspension's ability to bottom out. If you don't want to spend money on another new set of fork springs (which you probably need), the cheaper option would to just try running thicker viscosity fork oil at the same oil level.
