So many hints dropped out in this chapter.

So, the reason why the Reiss family posses a higher authority over the walls than the King and the Cult itself, is because they are the ones that utilize their power to keep the Colossal Titans (in the walls) in check ? Is that also why they constantly keep an eye on their descendants and why they reduce their numbers, so that there won't be a conflict between them giving different commands to the Titans ?

So Titans are his true love... awkward :p.

So the Walls, or the Colossal Titans in the walls are roting and in another 100 years will become useless ? Or did Levi meant that they contaminate the air within the cities ?

There are still many undiscovered memories within Eren. Looks like his mother that was eaten is not his real mother, also his father the doctor, also might not be his real father. He also might have a sister it seems.