Thats fantastic news.
I'm happy with with it though - it's exactly the house I would want to live in so I'm not going to change it. I might make the cellar a separate cell though as it does have a lot of items in it - this at least will reduce the amount of processing going on and I removed all the lights, I feel the candles and fireplaces make enough light without adding more.
Sounds like mission accomplished. I probably wouldn't worry about making it a separate cell though. If the vanilla cell had any roombounds+portals they might have copied themselves over, if this is the case everything should be nicely optimized so no need for additional cell. If not its worth learning http://www.creationkit.com/Bethesda_Tutorial_Optimization.
With regards to using a lot of bookshelves, I get no performance drops in the house but I do understand not everyone has a monster rig like me.
This is good to know, I by no means have a monster rig but my own house-mod will feature a fairly beast library room with many, many bookshelves so if they don't seem too demanding I shouldn't anticipate
many issues

. I digress, I don't want to go off topic.
If you're happy with the result that's something the best of us aspire to!