There's generally room for improvements in gear, but assuming you have good gear that's fairly light, such as our Soto OD-1R stove that weighs 2.6 oz. It works well and is light and compact. Is it worth finding one that weighs only 2.1 oz assuming all else is equal?
Nope, half an ounce is too immaterial for ME. I think the difference in weight vs. performance/stress of the body is a placebo effect. Assume a user has 15.5 pound backpack for one weekend and has a 15 pound pack for another trip the following week. The difference between the two packs is the stove. Do you think if he knew the final weight of his packs that he is likely to complain about joint pain during the weekend he took a 15.5 pound and vice versa? Assume each weekends were the same route and all other gears remain the same. If there is a scientist on here that like to conduct this study, I'm willing to be the guinea pig.
I don't think one particular small item, using your example, will reduce your weight if all others remain the same. You have to do a huge overhaul to reduce the material weight of your pack. I've carried a 40 pound pack before.. Now, my weekend (3 days) are averaging 25 pounds with food! I'm using different sleeping bags, new backpack, two new shelters that are lighter, new water filter, different stuff sacks, different clothes, and less miscellaneous clutters. Experience plays a good role as well since you know how much food, clothes, etc., to take. My winter weight is higher because I need the insulation and I'm allergic to down. I don't have the dough to shell out for very high quality and clean down. (Doctor may have a theory that those kind of down will not cause a reaction because they have been cleaned, and that just a theory I could still feel like crap.)
I think when your little girl gets older you can get a significant weight reduction. I applause you to introducing her to the outdoors.