I get to the Catskills a few times each winter for ice climbing and backpacking, and have been doing so for 5 years now. Given that, I'd critique your gear list as follows:
I have been up to my waist in powder many times when ascending or descending one of the Castkill peaks. A trail shoe is simply not sufficient for me in such conditions. I use insulated mountain boots. I assume you know your feet, but be prepared to have them IN snow, not on top of a packed trail (which may occur- depends on the day).
Also, the Northern Lites are wonderful on flat or gentle slopes, but can turn into toboggans on the steep. Once while I was descending the trail from Slide to Cornell my front foot (attached to Northern Lite Backcountrys) flew out straight while my rear foot shot backward. Evidently, I CAN do a perfect split. A snowhoe with more traction is a better bet, or also bring some aluminum crampons.
I've used my Marmot Helium with good results in the Catskill winters, and I have also froze in it... for me, the bag leaves very little margin for error. I usually take a zero degree bag, but you might be fine with the insulated clothing.
Take wooden matches along with your lighter- if your hands are cold or numb, a lighter can be very hard to use.
Be aware that Gatorade bottles can melt if you pour boiling water into them... so use the platy (is the mouth wide enough?)
I'd take another pair of liner gloves. I usually use powerstretch liners, then my softshell gloves, then an insulated overmit if needed. The liners tend to get damp, and so I dry one pair next to my body while hiking and wear the other.
Maybe extra batteries for the headlamp... don't know if I'd take a pack liner... no book? (the nighst are looong)
I notice that your only windproof/snowproof shell is the Paclite jacket. I use and like the Celestial, but I'd sweat buckets wearing that while ascending many Catskill trails. I prefer a super-breathable, hooded jacket that provides wind resistance and is snowproof. I have used Schoeller Dryskin and Patagonia's softshells for years and haven't worn a hardshell in winter for many seasons (except for sun baked ice climbs that are practically waterfalls).
Take my comments for what they are worth- internet advice. Regardless, be sure to get there next winter as it is really a fantastic experience.