Stress cracks can be OK. Just make sure that they run parrallel to the limbs lengthwise and make sure they are not too numberous, long, or connect to each other. They mostly appear at the fadeouts.

FWIW, I have two 60's Bears, one 70's Bear (well it's my son's) and a 70's Schulz longbow that all shoot fine.

I's also say to stay in the 45# range for your first. If you are going recurve, I wouldn't go shorter then about 60" and longbow about 66".