How would this appease him for more than a hot minute?
Speaking strictly FOR ME - I would not cut him an ounce of slack where the taxes are concerned because it can make an enormous difference in your refund. When you file separately you show your intent to be separated from him fully, including his liabilities & income.
If you meet the criteria to file Head of Household then I would really, really consider it. (provide more than 50% of the care for the children, had custody of them more than 50% of the time.... etc.... key word here is MORE... not Equal.) Just make sure that you can PROVE it if questioned. (receipts, bank statements)
Have you worked the numbers yet? How much do you gain/lose with the when you file using different HOH vs. Jt?