you've a very difficult task at hand. A deep sink mounted close to the
wall makes it very hard tighten the nut.

Comfort (as much as possible) is important to getting this done.

I hear you on the collection of sockets & wrenches that will NOT fit or
provide very little leverage. BTDT

Having a helper to hold the top assembly in place would help. Also
clock the faucet at about4 or 5 o'clock so that truing up the faucet
body tightens the nut further.

You get it close to tight & the helper (or you after switching palces)
tightens it further

I recommend against removing the sink

cheers
Bob