Lowe Outback 70 (70 liter), a bit over four pounds, great straps/hip belt, simple bag, zero bells or whistles, just bag, straps, twin aluminum stays, top pocket, easily would hold I'd estimate 40 to 50 pounds, and comfortably. Also easy to find used for probably 50 dollars. Solid materials. It's very light for being made out of heavy materials with thick hip belt. I picked one of those up used for cheap a while ago, perfect shape. Doubt I'll use it though, but it's nice to have the option if I need it. Oddly, the new Outback 65 weighs almost a pound more than the old Outback 70.
I just got a Lowe Zepton 50, 2.5 pounds, I had no problem fitting 8 days of food into it, I could easily have gone to 10 days. And I am not an ultralight (UL) backpacker, just a regular Light one (L). That was with a tent and a synthetic sleeping bag too, and an extra set of camp clothes, and a fleece jacket. And a prolite pad and Gossamer gear 1/8 pad. If I really worked at it and didn't need a bear cannister, I think I could go 14 days with that pack, the first day or two wouldn't be super comfortable but after it would be fine. I just noticed that Lowe now has the Zepton XL series for longer backs, so that's a good range of fits too.
Cost, about $100 on sale,, maybe $120. I can't really see any way I'd need more room than this has. 35 pounds is I would say about the max weight it can do comfortably, maybe a bit more for the first day if you really wanted to push it. Very comfortable, 30 pounds were no problem at all, no discomfort.
They make a bigger one too, the nanon, which I think goes to 60 liters. That also comes in an XL size for longer backs, as well as being bigger, but seems to be rated at the same weight, so I'd guess that's a choice for bulkier loads.
Maybe re-evaluate how you are doing your food?
Also, the ULA Circuit main body at 2400 cubic inches is 40 liters (2400 cubic inches in liters: 39.3289536 - when you want to do liter/cubic inch conversions, just type in google: x cubic inches in liters), and I assume because you have to roll up the top some of that is actually not really used. The Lowe Zepton is 50 liters, period. That would explain why I can easily get 8 days of food into it when you are having problems fitting in less. That's also one reason among several I did not get the Circuit by the way. The Zepton top lid inner and outer pockets probably hold 5 or more liters, not sure, but I don't believe those are counted in the total, that's also very useful. If I add in the capacity of putting on some stretch cord to create basically a back pocket, then I could pretend that the Zepton is a 60 liter pack, or whatever, but I don't do that (pretend outside pockets are part of the capacity, that is, I did add stretch cord to the back).