You know what it means to say supreme court justices will serve during good behavior? It's the quaint old way of saying it's a lifetime appointment. And why were they given life tenure? To secure their independence from the other branches, and from the democratic will.The framing fathers were anything but naive. Good behaviour was always meant to be upholding civil conduct to the position while avoiding all high crimes and misdemeanors. It's one of those "self evident" terms, something purely analytical folks have troubles grasping. They try to attempt to embellish on it when it says what it means and means what it says. When we were 5 years old we were told by our mommies and Kindergarten teacher to be on our "best behavior". I believe we know this means: "don't do anything illegal or stupid". The framing fathers never put term limits on any position. They didn't say Congress couldn't limit terms either.
The 10th amendment should be scrapped, and replaced with the earlier version that failed to pass--the one that said those powers not EXPRESSLY DELEGATED to the US belonged to the states or the people.Why? The doctrine is plenty sufficient for all intents and purposes as it is. It sounds like you would like to see the states having more sovereign authority. If that's the case, you should be looking at Amendment XIV. It ultimately gave the federal regime more sovereign power as it ensured anything at the federal level was forced down the throats of the states, including the Bill of Rights, all tax structures, currency, and any other Constitutional statute limiting federal power prior to its ratification.
It's clear from the last two paragraphs of your post that you favor the "living constitution." Because the "living constitution" doctrine is nothing more than a description of what happens when Article 3 powers meet implied powers.
As for the 14th, sure, throw it on the pile. Then light a match.