(Really, it lasts long enough for a person of average metabolism that what you experience in the evening isn't even the withdrawal, but just the tail-end of the dose, where there's slightly less of it. To experience the withdrawal, you have to stay up ~18 hours after taking it. Even then, from the few times I've had to stay awake for other reasons, it's still what I'd describe as "gentle"; but it does do interesting things to your dreams when it hits while you're sleeping, until your brain gets used to it. Personally, my dopamine-crashes-during-sleep gave me dreams with the exact visual character of Zdzisław Beksiński paintings. Oddly, no emotional affect associated—such visuals are not scary or unsettling, as they "should" be—they're just... what your brain is doing, trying to suddenly elevate noisy sensory data to salience and ignore the model saying "you're sleeping, that stuff is meaningless." Like an extremely low-light picture causing noise on a camera sensor, crossed with DeepDream processing.)

What you describe can be mostly from physical stress of being stimulated all day. Dexedrine, Vyvanse, or methylphenidate might give you a better ratio of cognitive to physical effects. Supplementing with a non-stimulant medication might help with your symptoms in the evening and also let you take a lower dose of amphetamine during the day. There's evidence that some supplements, like magnesium, can reduce adverse effects from stimulants. You probably already know this, but it's important to eat enough throughout the day and often hard to do that.

Magnesium is great, I take it throughout the day. L-theanine helps with the come down as well.