I'm not against the attempt at stealing at all, I also think your patterns might come into effect here. Have you been pushing to steal big blind numerous times without getting caught leading to the assumption all your doing is trying to steal and not putting the fear of a strong hand in? I just don't think this is a risk worth taking, with this level of blinds taking the 600 is not going to matter as much as the risk of him doubling up off such a poor starting hand with the realization that he's going to (assuming he's reasonable as you've said) push anything respectable anyways.