I agree with what you said but I do have one question; before Congress decided to include the payroll taxes as part of the “General Fund”, where did those receipts go?
Treating SS, etc. receipts as a part of the general fund was an accounting trick designed to hide the real deficit numbers because in those years the FICA taxes brought in more than went out in payments to retirees and others. The excess funds were simply spent like any other tax receipts, both before the accounting change and after.