That's a pretty slick kit really. You've pretty much done a good job of putting this together. Everything from here on in is nickle-and-diming it to reduce the weight.
A new sleeping pad would be pretty good. I am a slide sleeper as well, and am not really comfortable on the z-lite pads either. I have a similar pad, a big agnes insulated air core size regular: 24 ounces and worth every gram.
I just picked up a neo air x-lite small, 8.1 ounces with stuff sack and repair kit. I've only spent one night on it in my living room to test it out, and I was comfortable enough, so it might be an upgrade option for you.
If you have the sewing prowess and willingness for a few days of work, you can put together an M50/900fp down quilt kit from thru-hiker and put together a 13-14 ounce quilt.
With $300 you might be able to just squeeze in a Neoair X-lite and a MYOG quilt, or possibly a used Neoair and making a quilt. Doing so would drop roughly 22 ounces from your kit.
The other big ticket item would be shelter... but the contrail is pretty sweet. Use the contrail for this year, sell it, and upgrade to a lighter shelter next year perhaps.
Anyway, just my 2 cents.