I would be extremely careful with the selenium. Don't contaminate anything in your kitchen with it. I wouldn't even use the stuff in my kitchen.
I wouldn't do much else in my kitchen long term, but sometimes it's unavoidable
When I do use the kitchen sink, I wash it and the surrounding areas very thoroughly and try my best not to spill anything. As for chemistry I have to admit I just dump it down the sink (ilford rapid fix, ID-11, and stop bath).