rc51kid
You might already know that many here (with 357 mags) have indicated that their chambers are long enough (common with Handis) to accommodate loads using the slightly longer .360 Dan Wesson case. You could do a chamber cast to find out if this is the case (pun intended) with your 357mag, and if so, this would allow some improvement in performance when you handload.
Also, have go at the search feature to find previous threads about using .360DW brass and loads in a Handi.
And, to simply answer your question: Yes, I think a 357 mag with good shot placement and bullet selection would be just fine at 100 yds. I hunted for a few years with different rifles chambered in 357mag; a Rossi Model 92 clone lever action, a Marlin 94 lever action, and a Handi in 357 (I used factory rounds in those days, so I don't have any first hand info to pass along regarding handloads).
Though I never actually shot a deer at 100 yds, (it was rare where I hunted) I was quite confident that I could put meat in the freezer if I had to shoot that far.
Currently I have a 357 mag, as well as a 357Max (factory) Handi. And since both are relatively new to me I haven't yet worked up specific hunting loads for them. When I do I will have no concerns about either at 100 yds!
Cheers
Kerry