After more dialog, the acquirer updated the offer with a $50K rev share minimum at the end of year one and $25K rev share minimum at the end of year two with the sentence "assuming you are still employed with [acquirer]". The base salary still remains $25K lower than my current base salary.
Also, my current employer just informed me that they will not be providing / continuing my pay during my paternity leave; I will just receive FMLA coverage and PFL through the state of California. Due to this, I did ask the acquirer for part-time work so we identified a project I can work on but they haven't provided any payment / salary information.