At one point you mention that you plan to go NOBO and start in March. Early or late March? It might make a difference in the tent you select insofar as shelter space is pretty freely available for an early March start, and perhaps less so for a late March start. I started in late Feb in 2010, and very rarely used my tent, sleeping most nights in shelters. In that context, a more minimal, "it will do" lightweight tent is a better choice.

At 6'1", and overall larger than me, I can't help you too much there. Indeed, the lightheart designs solong variant might be a good choice if you're willing to spend some money. Something like the SMD Wild Oasis is a great choice for someone doing mostly shelters, but not so much I think for someone your size.

The lightheart tents are great; I hiked the CDT last year with a cuben lightheart solo, and it held up very well. I would not suggest spending the money for a cuben tent, however, unless you're pretty confident that you actually will spend a lot of nights in one.

Perhaps a hybrid approach: just carry a tarp for the first month or two, then switch to something that is bug proof after that. In bad weather, stay in a shelter if possible, but have the tarp as backup.

I wouldn't think in terms of cold weather. Okay, a lightheart tent might be a little warmer than a pure single-walled tent, but don't factor that in much. You're much better off dealing with cold via sleeping bag and puffy clothing than with a (heavier) tent. Especially, again, if you think you might sleep much in shelters.

Packs: ULA packs are pretty popular for thru-hikers, and especially if you have it in your head that you might do more than one such trip --- pretty durable for the weight. One of my hiking partners retired his catalyst after 5000 miles of backpacking and it still wasn't in really bad shape. I did half of the AT and all of the CDT with a circuit and it's still in great shape. A good mix of features vs. weight IMO.