is the windows version of the new fork going to be released anytime soon?
You mean binaries? I am a bit too busy to build binaries for non-release beta versions. You can still run from source on Windows, though.
If I am running the old 16.0 version of p2pool, am I still going to be part of any blocks that are discovered by the new fork? If so why then is the calculation of the rewards different on each separated network?
No.
It would appear beneficial to the cause of p2pool miners if we combine the hashing power between both networks just so we can actually get closer to finding a block
Agreed. Before we can merge the two pools, we need to get the 1mb_segwit branch tested on testnet and the bugs that prevent it from working with altcoins fixed. Can you help with that?