Step through bikes are going to be heavy just because of the structural design challenges posed by not having that top tube. So in a budget bike 25 - 30 some odd pounds should probably be expected. I don't even think I've seen a high dollar step thru lighter than your current 25 pound bike.

Since you aren't riding those hills to see how quick you can get up them, then probably concentrate more on a bike that has a wide range of gear ratios. Especially low ratios to let you easily pedal up those hills without grunting too much. Weight is less important if you aren't trying for a KOM.

A bike that has one of those kickstands similar to some motor cycles that has a leg coming down on either side might make your bike more stable when loading and unloading. Don't remember what they are called but I have seen them on cargo bikes.