Is there a way to add "Show All" to the list of Visible Rows

The Max Number property affects all queries on the model.  
- When you load a page - that’s how many records will be retrieved.  
- When you execute a filter or a server side search - you are actually running another query to the server - hence the Max Number affects how many you get back.  
- When you hit “load more”  you get another incriment of records in the size specified by your Max Number. 

The only exception to this rule is client side search,  which filters only on the records currently in memory.

And yes - eventually your queries will have problems as you get more information in your system.