Get out of there.

Your mental health is far more important than some empty promise that "things will get better".

Hint: they're not going to get better, because the problems you have are orthogonal to how the business operates. As long as they can remain profitable, they'll wring every last drop of productivity they can from you and replace you as needed.

They might not state it as such, they might not even know they're doing it--but the fact that "things will get better" date is a fiscal year should hint where their priorities lie.

Get out--you don't owe them anything.