Salt, I have a somewhat easy fix for the hammer.
Go to the store and find a smaller handle replacement, one that feels a little small in your hand. You're gonna cut the handle in half and epoxy it to the hammer tang then install brass pins.
Lay it beside your old hammer and mark the length how you want it to lay on the tang.
Build a jig to hold the handle so you can cut it down the middle on a table saw or a bandsaw would work best with a thinner cut.
I would drill holes in the handle part you're not gonna use to screw it to the jig to hold it steady while you cut it in half.
Lay the handle on the hammer tang and mark the tang for 2 holes to be drilled to install brass pins. You should be able to find 3/16" brass stock if not then find 2 brass bolts long enough to cut off the threads.
Lay each handle half in the tang where you want it mounted, clamp it down and drill those handle holes 1/64" smaller so the brass pins fit snug. Repeat for the other half of the handle.
You should be able to find a 2 part epoxy in hardware stores, use that to glue the handle to the tang. Test fit it a few times to make sure you can get the pins aligned easy before the epoxy dries.
Let it cure and cut the pins to length and clean off any excess epoxy.
Fill in the gaps with more epoxy, you might need to do one side at a time to let it set so it doesn't run out.
It should be a fun little project, it seems like a lot but it will go fast.
Watch this video for installing a handle on a knife and you'll understand exactly what I'm trying to explain.
https://www.youtube.com/watch?v=R-iM1_WFMAk