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The time variability and spectra of directly imaged companions provide insight into their physical properties and atmospheric dynamics. We present follow-up R ∼ 40 spectrophotometric monitoring of red companion HD 1160 B at 2.8–4.2  μ m using the double-grating 360° vector Apodizing Phase Plate (dgvAPP360) coronagraph and ALES integral field spectrograph on the Large Binocular Telescope Interferometer. We use the recently developed technique of gvAPP-enabled differential spectrophotometry to produce differential light curves for HD 1160 B. We reproduce the previously reported ∼3.2 h periodic variability in archival data, but detect no periodic variability in new observations taken the following night with a similar 3.5 per cent level precision, suggesting rapid evolution in the variability of HD 1160 B. We also extract complementary spectra of HD 1160 B for each night. The two are mostly consistent, but the companion appears fainter on the second night between 3.0–3.2  μ m. Fitting models to these spectra produces different values for physical properties depending on the night considered. We find an effective temperature T eff  =  |$2794^{+115}_{-133}$|  K on the first night, consistent with the literature, but a cooler T eff  =  |$2279^{+79}_{-157}$| K on the next. We estimate the mass of HD 1160 B to be 16–81  M Jup, depending on its age. We also present R  = 50 000 high-resolution optical spectroscopy of host star HD 1160 A obtained simultaneously with the PEPSI spectrograph. We reclassify its spectral type to A1 IV-V and measure its projected rotational velocity |$\upsilon \sin i$| =  |$96^{+6}_{-4}$|  km s−1. We thus highlight that gvAPP-enabled differential spectrophotometry can achieve repeatable few per cent level precision and does not yet reach a systematic noise floor, suggesting greater precision is achievable with additional data or advanced detrending techniques. [ABSTRACT FROM AUTHOR]