Can one quit at any point and does it get more difficult up the ranks?
You can quit at any point. Just stop going to meetings and paying the annual fee. Nobody will forcibly drag you there. Some would probably worry about you and check on you, as friends, but they would leave you alone if you say you've had enough.
What is the symbolic significance of a black n white checkered floor
Duality, balance, extending out to eternity to mean the whole world as a lodge. That is my understanding from our discussions, though. None of it is passed out and studied as a book.
and horses?
I have never seen horses in relation to Freemasonry.
Why are the ranks and freemasonry shrouded in mystery? I know you alluded to it being like a school and not wanting to get ahead of yourself or find out answers before working it out. However, like schools though, everyone's path/ journey with learning or the knowledge is different...regardless of whether we knew the curriculum and expectation at the end.
You said it: Everyone's path/journey is different. The way it works in Freemasonry is that you question and work on different topics in each degree. So you are exposed to ideas one by one, and you slowly work your way through them through that year or so with discussions, speeches, questions. If you had a book in your hand that told you what you would see at each degree's ritual, it would lose its meaning and effect on you.
The secrecy is what gives freemasonry a bad image imo.
It's not secret, it's esoteric.