Welcome aboard! We love our 2012 23B. I have done a lot of modifications.
Like to hear more about your new drain valve. I'm thinking when mine dies, to install something like yours. Like to know more about the parts and install.
Two other favorite mods. Remove the panel under the sofa. Cleaned up the utilities under there. It now stores shoes and a case of water.
Other favorite item, complete rebuilt the front dinette. It now has a full pass through storage. The drawer is gone, but the face is there. You can see in my signature this mod. There is a bit more to it than that.
As for October camping, do it all the time. Typical last campout is MEA weekend. Most years it gets down to the mid to low 20's, so far no issues. All the plumbing is inside except for the tanks. To help keep the pipes warm, we just keep the cabinet doors ajar, to let a little more warm in. I would recommend adding a couple electric mattress pad heaters to your fall gear. Outside edge of the bunks can get mighty cool on a 20 degree morning.
I do keep 2 gallons of rv antifreeze in the garage. Most years it is not an issue. There have been a few years, mid week I have blown the water lines clear, and added a little antifreeze to the traps. If the heat is not on, higher risk of damage.