He says he will pay more once I've agreed to his settlement offer
It is unfortunate you do not have any witnesses that heard your stbx say that. It rings of blackmail and certainly would raise major doubt that he is unable to pay more, right now.
He is also financially abusing you but more so, the kids.
Do you communicate with him at all by email? Do you think you could ask him to confirm and clarify by email or text that he really means it when he says he'll pay more once you agree to the paperwork and also how much more he'd be willing to give?
When added to your H's behaviour around the settlement and his spending elsewhere, the pizza now really seems like it's bribes and attempts at him to prove he's helping you and the kids more than he is legally obligated to.
As much as that may not feel good to have him over, it might also be used as evidence that he CAN give more. Pizza isn't necessarily the cheapest, nor most healthy meal that he could otherwise be providing for the kids. Again, it could help expose manipulative behaviours. At least put doubt into the mind of the courts.
