How to determine the symbol rate of a 2-FSK signal?
One approach could be to perform an FM-detection step (e.g. an atan2() operation followed by a first-order difference) to transform the waveform to measurements of the approximate received frequency versus time. Your FSK signal should then look like a binary-modulated baseband waveform. Then you can apply a nonlinearity to the signal to induce a discrete frequency component at the unknown symbol rate. This component can then be identified by spectral analysis of the signal after you apply the nonlinearity. Many different types of nonlinearities can work for this, including absolute value, squaring, and magnitude-squaring detectors.

If you're doing a literature search, the terms you might want to use would be blind symbol rate estimation. That implies the estimation of the symbol rate without foreknowledge of the signal's structure.