WHY is a prez allowed to take action without Congressional approval sometimes? That blows to he** out of a check-and-balance system. RIGHT?

If the system of checks and balances manages to survive federal courts legislating from the bench, it can survive anything. Let's not cherry pick our areas of usurpation of powers that were  granted to each branch under the Constitution. God knows Congress has been stealing power for themselves for decades at the expense of states governments.