Ok, good news! Nitrites and nitrates are off the scale, ammonia is down to 2.0!!! According to the fishless cycle guide, this means it's time for a 50% PWC. We brought in every bucket we have, filled with tap water to warm up for tonight.
I'm noting that the water is still crystal clear, but has a very slight green-yellow tint to it (such as looking through the tank at the wall behind). Guessing this is normal, to a point.
Plants are dying off ever so slightly, guessing this is due to very high nitrite/nitrate levels, and normal acclimation.
Also - the glass was cut for the tops...but it was cut incorrectly!! ...again... They cut four squares instead of four pieces that fit into two squares (obviously I gave them the exact piece measurements, not weird descriptions like that). Guess something was lost in translation. At any rate, two of the four squares they gave me fit the top openings perfectly, so I just need to drill/grommet for the overflow siphon tube and silicone on some handles. I noted that within seconds of placement the glass had misted over with condensation...so this should help. Also appears to be helping keep the temperature in...tank is back up to 78.7.
Tonight, water change (which will be a rather difficult exercise...), dose ammonia back up to 4, check pH, and continue the waiting game. In theory we are very close to the point where ammo/nitrite disappear overnight and the cycle is complete.