Hi Nich!
I'm just spit-balling here, so take what you want from it:

When weather permits, take just the rain fly or just the tent.
If you're not already, use a tyvek ground cloth.
You sit on the groundcloth instead of a camp stool.
Ditch the Nalgene for a smart water bottle (surprisingly durable)
By all means, bring enough water, but 4 liters?! That's reasonable if you mean for the three of you combined. Correct me if that's what you meant or not.
Consider taking less toiletries with you (but don't skimp on TP!)
If a bear canister is not required in your area, go with an UrSack or other bear bag.
Consider leaving some/all of your extra clothes at home or choose lighter ones.
Modify your existing gear (be safe).
Share the load with your BF.
Get a dog pack so your dog can carry his/her own food and water.
Try using a homemade alcohol stove or going no cook.

You're already doing the best thing possible - research!

Hope this helps. Cheers!