Congress can pass any law it likes! And the courts can interpret it anyway it likes!
This is true and this is a difficult discussion, as you both are essentially correct.
The Constitution, as the great patriots that wrote it, is as humans. Not perfect.
Thus, again, it finally rests with good and evil, and the qualities of men.
The SCOTUS can be reigned in by regaining the Congress and White House, and packing the court.
Additionally, the SCOTUS is the only Constitutionally required Federal court, the rest exist at the pleasure of Congress.
SCOTUS was intended by the framers to be a trial court. In a usurpation of power, SCOTUS has shirked that duty. Threat that they would be the only Federal court in the land might scare 'em straight if packing doesn't.