Not giving money to researchers is hardly a criminal matter. Of course some congressmen could propose impeachment anyway, pretty sure some already have, but they don't have the numbers to kick him out of office so it's just posturing for their constituents.
It's not immediately clear to me how we should read the Constitution on that question, but the Impoundment Control Act seems to explicitly include "delay" alongside "withholding" in things that it might be forbidding.
His disregard with what Congress already signed into law is troubling, but he might find sympathy from members who were not in Congress before, as well as members who didn't sign the legislation he's overriding.
