[Nexus 7 (2013) Q&A] sfhub:
fastboot.exe is a tool used to communicate with the bootloader. It is packaged with adb.exe along with 2 windows libraries. It does not often change. Normally you download the sdk/platform tools to get fastboot and adb, but that introduces more complexity than necessary so I just found you the most convenient zip file that included those files. The reason that archive listed the version # is not because of fastboot, but because the included .bat install scripts reference the system images for that version, which understandably have the version # in their filenames. If you look at the addon zip file I pointed you at, you'll find fastboot.exe and the two adbwin*.dll files. Those are universal and do not change with ROM versions (they do eventually change over time, but it is only when they change the USB interface)

There are many ways to do the same thing. Sometimes you need USB debugging enabled, sometimes you don't. You can reboot into bootloader using

adb reboot bootloader

or you can also do the same using

turn off tablet, turn on by press/hold Power+VolDown

One requires adb the other does not.

You can search for "version discussion" for example in google, search for "JSS15R discussion" or "KRT16S discussion"

You don't actually need a new add one file for each version. Just copy the fastboot.exe and adbwin*.dll files into the new factory image folder. If you want to flash the factory image while keeping your user data, edit the flash-all.bat file and remove the "-w" flag for the fastboot command. That is what the "nowipe" option is doing for you.

You can do that also, I just like to keep thing clean and simple. Instead of dumping a factory image file you will probably only use a few times into your platform-tools directory then forgetting about it while eating up disk space, IMO it is easier to just take a few files you need to install the factory image and add those to the factory image when you extract it.

Also I recently found out the latest platform-tools fastboot.exe no longer works with the factory images anymore. It will give an error that system.img is missing even though it is not. I figured it was less trouble to point you at a known working fastboot.exe than having you figure out the sdk you just downloaded doesn't work and you'd have to figure out how to get an older version.

If you leave the bootloader unlocked, then you don't have to lose your user data (by unlocking again) to fix problems. Leaving it unlocked might expose you to someone stealing your tablet and bypassing your lock screen, but IMO it is far more convenient to leave it unlocked. Nothing will break by having it unlocked.

I would suggest you try flashing JSS15R

http://xdaforums.com/showthread.php?p=45671279#post45671279

That will probably work ok. I would suggest you run this for a couple of days to make sure everything works and also so you have a baseline comparison of the touchscreen performance.

After a few days, if it does work, and you are willing to take a risk, try flashing KRT16S again (this time you'll be keeping the ts10 touchscreen software).

KRT16S can be flashed from here:

http://xdaforums.com/showthread.php?p=47640458#post47640458

---------- Post added at 12:14 PM ---------- Previous post was at 12:12 PM ----------

The reason your OTA is 245.2mb instead of 253.1mb is because this OTA update is patching JSS15J to KRT16S.

The previous one was patching JWR66N to KRT16S.

Since the starting points are different, the files included are different (and will differ in size)

---------- Post added at 12:15 PM ---------- Previous post was at 12:14 PM ----------

OTA does not care whether your bootloader is unlocked or not.

Factory image as provided by google at this time must have your bootloader unlocked.