I believe your deducations may be correct regarding the stepped PL053 & micrometri PL043, based on google & some reading. Note that some of the information I read was for overseas models which may have different specifications. Best to call the people you mentioned to ask and see if they have them in stock.
From my experience the non-sponsor you mentioned has extremely slow response times if contacting by email, up to a week or more on average. Compare that to Chris from Talk Coffee who, in my experience, has a response time of under 5 minutes! Guess who I bought from when the time came!
These grinders use the Lux-type burr set which is used on number of other grinders including the Ibertal Challenge which is available from several sponsors and also has micrometric adjustment.
A new player on the scence which has been described as a category killer by at least one sponsor is the Breville BCG800 whic is in the same price category. I guess the only downside is that it may look a little too modern sitting next to a La Pavoni lever.