yes, you can split the developer lots and the blix lots. I would recommend take the part B ( I think that is the one with the developing agent ) and transfer it to a glass bottle that leaves little air space, or top the space off with (nitrogen/butane/propane - research past posts on this issue). The developer kit that I bought was to make 5L, and stored this way it is still viable tat I continue to mixing up from 3 year old concentrate (stored in a cool dark place most of the time).
The bleach fix and replenisher is like it says. Yes, its ok. The dilution instructions are on the box. It too will last a long time, longer than the developer once mixed, but again, mix up partial quantities in the right proportions.
Google Kodak Z-130, and you will find more RA-4 information than you ever could imagine.