Can I cut Amphetamine Salts in half?

If it's the immediate release tablets, yes splitting is perfectly fine.
If your dose is once daily, I have found splitting the tablet and taking half in the early morning and the other 4 hours later is optimal.
The half-life of this pharmaceutical is about 4 hours but if you split the dose the blood levels gradually decline rather than spike up then rapidly down.
This will prevent what many describe as "a crash".
I for one always advise this for the once-daily dosing of amphetamine rapid action products that are Not time released.
Thanks for the question

Yes, I actually have to take it with one of the Adderall IR pilla split each dose (1 & 1/2 tabs per dose). If it's an immediate release tablet, you should be okay, although everyone is different! If you are still worried, please call your doctor asap.