Bowhunters regularly kill deer with 35 lb longbows. Anything you use for small game is going to be overkill. Personally, I find nothing more fun than taking out my recurve when small game hunting. You can draw and shoot much, much quicker. Besides, it's just plain fun.

The reason you don't want to use the same compound for small game, is that the arrow required out of a 58 lb draw is not the same as what you need out of a 70 lb draw. You can go out an buy two sets of arrows - one for small game, but then your sights are not correct. For me, it's far easier and more enjoyable to shoot different bows for different purposes. You may even want to leave your old bow setup for small game.

You may want to think carefully about that recurve/long bow option. Good used ones can be found cheap and shooting them at small game is absolutely addicting.