Your temp profile seems odd with you cooling a lager towards the end of fermentation.
Cool then warmup to a diacetyl rest at the end would be more typical, then cold crash.
Regards of pressure low at the start as you started cool anyway. I tend to turn the spunding valve up about half a dozen points from final with a target pressure to match my target vols. This could be 20+ psi. Once ferment and D rest finished then cold crash.
Given this should be a few weeks pressure and vols will stabilise.
The pressure will drop during this as CO2 absorbs.