Partial phase reconstruction based on a confidence domain has recently been shown to provide improved signal reconstruction performance in a single-channel source separation scenario. In this paper, we replace the previous binarized fixed-threshold confidence domain with a new signal-dependent one estimated by employing a sinusoidal model to be applied on the estimated magnitude spectrum of the underlying sources in the mixture. We also extend the sinusoidal-based confidence domain into Multiple Input Spectrogram Inversion (MISI) framework, and we propose to re-distribute the remixing error at each iteration on the sinusoidal-signal components. Our experiments on both oracle and estimated spectra show that the proposed method achieves improved separation results at a lower number of iterations, making it as a favorable choice for faster phase estimation.