First,
I have no idea what limited presidential immunity has to do with any proposed reforms of the judiciary itself. This is just a response to a single recent opinion -- and is entirely situational. By that I mean that it's all about Trump and the various legal things that came his way as he ramped up another presidential campaign. Ask everybody at some other period of time, in some other situation, and it seems entirely possible you could get precisely the opposite answers -- depending on who is embroiled in what at that time.
Second, I'm quite sure that
judicial term limits would require a Constitutional amendment. The Constitution specifies a number of terms of office. And, of course, the 22nd amendment specifies term limits for presidents -- which didn't exist prior to 1947. Given the absence of terms or term limits for federal judges in the ratified text (it only says good behavior), it seems obvious that Congress lacks the authority to do this by statute.
Again, this is also situational. And, no, it isn't a thing right now because we've determined after 30 years on the bench that Clarence Thomas is a crook. It's a thing right now because Democrats have lost their shit about the opinions being issued by the Roberts court.
Third, a judicial code of ethics may be a little murkier. The lower courts already have one that's imposed by statute -- and administered by the Judicial Conference (which was also created by statute). But the lower courts are entirely a creature of Congress by way of Article I, Section 8. The Supreme Court is its own branch of government. So
there are probably separation of powers obstacles here as well -- and it probably explains why the statutory judicial code of ethics has always only been only on the lower courts.
One wonders how Congress would react if the Judicial Branch tried to craft and institute a code of ethics on the Legislative Branch. Congress does this itself -- and for a reason.
Biden, Harris call for Supreme Court term limits