I don't know what to do, but boy do I feel where you're coming from.
Here are a few ideas. They might help, or they might inspire some other, better ideas:
The schedule change might be frightening/upsetting to him because it is upending his established order and he is lashing out and accusing you of lying in order to try to "protect" himself from this change. It might help to acknowledge what he is probably actually feeling and try to avoid getting sucked into responding to the angry outbursts.
It might help to remind him more frequently of the expected change. Like, if he made the agreement a week ago, tape copies of it in several prominent locations and then remind him multiple times a day until it happens. That way he doesn't have a chance to forget.
This doesn't address the bed situation, but I've had some success recently with solutions that let my son take care of problems on his own, for example, a small trash can next to the toilet for when he uses too much TP (better TP in the can than plungering the toilet every day) and a designated dirty laundry box next to his bed where he can put clothes he wants washed and he knows that I know to wash them without him yelling about them. (So far. Wish me luck.)
I've also been making a point to make time for daily love and kindness meditation for a few minutes every morning. This is a time that's just for us when we relax and try to practice good feelings so we'll have an easier time remembering those feelings later. (We've been doing this for about a week.)
I find that my son is more responsive and easier to talk to while walking than while at home, so if I have something important to discuss, I try to bring it up during one of our walks.
Good luck.