Wanting to use leftover pipe and fittings is commendable, but not a wise choice of material. The inside diameter of CPVC is something like a size smaller than other media such as PVC or copper. You are not draining potable water, so PVC would be a good and cheap alternative. I'm not familiar enough with the PB pipe to advice on exactly how to connect the PVC to it, but a neoprene sleeve with clamps on both ends would be one way assuming you can find the sleeve in the proper size. There may be some kind of adapter or combination of fittings that would work as well. Remember, there is no pressure in this line, so there would be no problem there. You need to understand that CPVC and PVC "glue" is not really glue at all. They are solvents that briefly liquify the top surfaces of pipes and fittings so when the pieces are joined the two surfaces blend together and form a chemical weld. Quite similar to metal welding. I can't give you specific information on oxy-bleach (is this Oxy-Clean?) but chemical drain cleaners of any kind are not effective on clogged drains in spite of what TV commercials would have us believe. You might try connecting a hose to the pipe and using water pressure to push the clog out.