The batteries should last about 6-9 months depending on your use. In terms of cost, check it out at your local store considering they use common batteries. On Amazon, you can get them for really cheap. Look up CR2032 battery
It's easy to clean, but with raw chicken I would always put something under it if you can't clean it with a lot of soap and hot water - it's just not worth the risk.
The battery life is pretty decent. I bought a 20-pack of generic low-quality batteries and I use it pretty extensively for several minutes each day. I usually only have to replace the batteries about once a month.
The fluid ounces are based on water. For example 7.2 fluid ounces of water is 7.5 ounces. The weights will not be correct unless the density is the same as water.
I don't know from experience but I don't see why not. It's not like it has any liquids or anything in it. I would just be careful not to bang it with the cutting boards. Anything electronic does not like to be banged around.
