Personally, I would not use anyone else's reloads, especially when you don't know who rolled them. Just too many variables. Why they are labeled handgun only is another question as well.
For coyotes, the .44 mag would certainly work, just awful big. You certainly don't need that much gun for a coyote. If you like the rifle and want it, with the possiblility of wacking a coyote now and then, well, go for it. Certainly will work. Any good factory load 180-240gr will work. I suspect the heavier bullet would be better if you wanted the hide, should pass right through without opening up.
If you are looking for a dedicated coyote rifle, I'd recommend a .223, .204, .22 hornet, or .22 mag. Flatter shooting and usually don't rip the hide all up.
Best of luck.