Contrary to the often repeated dogma of 10gpp, I don't think you're automatically going to blow up your bow if you shoot a light arrow. Some bow makers place an 8gpp minimum in their warranty statement, but a lot of archers have been shooting lighter arrows for a long time.
Given that you said you'd be shooting a 55-60lb recurve, I don't think you'll find too many popular hunting arrows that spine properly, and are too light, with a 100+ grain point and reasonable arrow length. (400 grains @ 60lbs = 6.6gpp)
Now, before I get my butt jumped here, I'm NOT preaching for the use of light arrows for hunting. My own hunting arrows weigh 10+gpp. The benefits of a heavier arrow far outweigh the loss of trajectory, IMHO. Also, if you shoot the same arrows for small game and big game, you don't have to compensate for the different trajectories.
You may be an exceptional shooter, but at the ranges I would take a shot at a tree rat, I don't see an appreciable gain in accuracy with lighter arrows.
To answer your question more directly, I would personally suggest no less than 400 grains, but a better suggestion would be to ask the guy that built your bow!