That looks good to me. I especially like the spreadsheet you used. That's slick.
As for weights, the cheapest and easiest thing to save weight on is the poncho. For $20, you can get a set of Dry Ducks at 10 oz.
I agree that the sleeping bag and jacket are areas where significant weight savings can be had. But the biggest potential for weight is your pack. You are getting down to near 20 lbs, so you can't have an excessive bulk of gear, and you can start to pair down the pack size and weight. For me, I was at a huge barrier I could not get past (25ish pounds). Once I replaced my pack, the rest seemed to come off easily.
There are lots of good packs to look at in the ±2 lbs range. I am particularly fond of my ULA Circuit, but also consider Gossomer Gear, Six Moons, MLD, GoLite and others.
As for your sleeping bag, I highly recommend you move to a top quilt. The provide a signifanct weight savings, but if you are in a hammock, it will enhance your hammock experience significantly. They are not cheap, but you can find a 20° top quilt in the 23 oz range, half what your current bag is, and much more comfortable and easy to get in and out of. GoLite has some good quilts, but I cannot say enough about Hammock Gear. Best products I have found.
Hope that helps.