Extreme lag and other problems after updating to KitKat 4.4 (S5)

I updated to 4.4 a few days ago and have been having a LOT of problems.  Most notable is the extreme keyboard lag.  I can barely type on my phone anymore which renders texting and many apps useless.  The screen is having a hard time registering my taps.

The screen will not auto shut off anymore even though a timeout is selected.  I have to physically turn my phone off.

Most of my apps are very slow.  An example - playing a game such as Disney Tsum Tsum, the screen is not registering my swipes and is freezing up.  Never had a problem with the game until the update.

My phone is also now abnormally hot after just a few minutes.  My 3rd party battery minder app keeps popping up to tell my the CPU is overheating.

Call quality has also decreased, not sure if this is related to the update or not, but ever since I updated, I have had people complain of not being able to hear me/saying I sound like I am breaking up despite having full service in 4G LTE.  Ever since the update, I have also noticed my voice echoing in all of my calls.

I haven't changed anything EXCEPT for updating to 4.4.  Really frustrated.  I had a brand new, perfectly good working phone that I was very happy with...and since updating a few nights ago, my phone feels like it's absolutely useless.  It is not performing the way that a very expensive smartphone should...

And don't get me started on the fact that the other carriers are rolling out 5.0 and we are just NOW getting this junky, bloated 4.4........

Can I go back to 4.2 if I do a factory reset?  Do I even have any other options other than a factory reset?  Will I lose everything?

By the way, Smart Network Switch has already BEEN off since before the upgrade...so please don't suggest that I turn it off.