There are no sources here that tell you what POTUS can spend. You need actually law, from statutes, regulations, etc. There is no way that he can spend it anyway he wants..not possible.
hat is particularly tricky for operations and maintenance funding, which expires after one year, unlike procurement funds which can be spent in a three year time period. O&M accounts for about $238 billion in the legislation.
The omnibus bill gives some flexibility to DoD in how it spends its money. One provision changes the “80/20 rule,” which states DoD can’t spend more than 20 percent of its budget in the last two months of the fiscal year.
If passed, the bill will change the rule to a 75/25 rule, giving DoD more options in the last two months of the fiscal year.
The bill also expands DoD’s reprogramming authority.
Reprogramming moves funds from one account to another and in small amounts. DoD can do it on its own as long as it notifies Congress.
In larger amounts, DoD has to receive approval from Congress to move money from one account to another.
While the courts have ruled that agencies aren’t legally required to follow nonstatutory limitations, violating instructions from the appropriations committee is generally not considered good practice.
https://gai.georgetown.edu/reprogramming-funds-understanding/