1. I don't know the figures for it, but a 36 HP steam boiler will run for 1 hour on 36 buckets of biofuel, generating 144MJ/tick. This equates to 144MJ/tick for 2 000 ticks, or 288 000 MJ /bucket. It's unlikely that the biorecator will be able to match this, but the capital cost (of steel and the heatup time) is hefty, and in order to account for this, you need to use all of those 144 MJ/tick. I would say that, when you are producing 36 buckets per hour, it's the way to go (after a while to build up a buffer, of course).
2. As far as I can tell, per single item, you are probably better with forestry (also uses bits like wheat, which the bio-reactor doesn't), but, if you can set up a diverse input, the reactor is the way to go (also don't forget the trick about jalier's net, quid and rancher for massive amounts of reactable ink sacs!). My current setup uses vanilla oak saplings, melon seeds, pumpkin seeds, carrots, potatoes and ink sacs and gets me more than is being used by 2 36HP boilers.