Welcome back.
Very in-depth analysis of your situation, interesting read.
Depending on the time you have at hand you can adjust your rental strategy on your current focus. Also consider the usefulness of cards at certain levels, as you already did, from the beginning, i.e. when does which stat increase or which ability comes into play. And do you make use of that ability at some point?
Just some random thoughts.
!PIZZA
RE: Is It Profitable to Rent Almost A Full Playset At Silver Level?