Multistatic phaseless synthetic aperture radar (SAR) is a novel imaging modality that offers advantages in reduced hardware complexity, operability at high frequencies, robustness, jamming resistance, and improved accuracy and resolution. Illumination diversity is a key facilitator in designing novel phaseless imaging systems for applications in optics, and with growing interest in radio-frequency sensing. In this article, we present a novel multistatic phaseless SAR imaging method using stochastic waveforms and the nonconvex Wirtinger flow (WF) framework that provides performance guarantees under sufficient conditions known to hold for certain random forward models. We present multiple variations of the WF algorithm including different initialization and regularization methods and study the tradeoffs between the performance of our algorithms with respect to the resources needed for phaseless multistatic imaging. Our extensive numerical simulations show that the waveform-diverse random illumination approach coupled with optimization-based reconstruction provides near-exact imaging with a limited number of transmitters and a single receiver, promoting our method for practical realization of phaseless multistatic SAR.