I dont know how you used TWRP to root, but if you already have the updates then you dont need them again, Yes updating to B10 will break root, it's ok though because you can reflash TWRP and have root and custom recovery again,
http://androidforums.com/boost-mobi...0-based-viii-ii-full-install-1-23-2013-a.html
On the third question, Yes again, it will wipe your data and install massive bloatware.
If you want a custom rom just flash noob VIII.II. That will give you all the updates without the bloatware, custom recovery, CWM not TWRP, and custom OC kernel. If, after that, you still want TWRP as your custom recovery, just flash that file. Link above.
If you do not want a custom rom, but the updates only without all the bloatware then flash the deodexed version of the update found here.
http://androidforums.com/boost-mobile-warp-all-things-root/675897-stock-b10-deodexed.html
Their is also another rom Based on the B10 update, fully functional and flashable found here.
http://androidforums.com/boost-mobile-warp-all-things-root/676102-b10-based-rom.html