Ok well good it fixed your windows as stable windows is half the battle in BF4 so its a start to get your BF4 working correct. Not fully sure this can fix your issue but it is worth a try as it has fixed issues for others, I am thinking this could fix your sound bug and maybe your FPS in game. ....
In my documents you will find a BF4 folder holding the game config files and screen shots. Put it in recycle bin or desktop then repair game and try BF4 again. But to give you a heads up you will have to re set all your in game settings.
Your FPS drop could just be settings in Nvidia control panel or a issue in BF4.... open NCP and on Adjust image settings with preview pick use my preference and set it to performance. Next go to manage 3D settings program settings add BF4 if not in already and make sure triple buffering and vertical sync are off.
Also what are you using to see FPS in game? Is it fraps or some other program? I made my own cfg to show fps in game so I dont need to type in anything or run fraps BF4 already is a hog lol so why run extra stuff .....this is how you do it..... Sadly I cant get in to work in BF3 :[ lol
1- open note pad
2-put this in the note pad..... perfoverlay.drawfps 1
3-when you make the user.cfg in notepad,change the file type from text to all. And
name it user.cfg
4-Put in .....:\Program Files(x86)\Origin Games\Battlefield 4
5-Also close Origin to put cfg in just to be safe :}
If this still does not work then this is my full post on how to fix BF4 when every other fix has failed to fully fix it. But it is a big pain to do and I am the first to admit that and I am not fully sure you need to do it so try the stuff above first. But if all this still fails then it is worth a try and yes this is everything I did to fix my BF4 lol big pain in the .... it was but it worked for me and a few others and some of it you already did.....
http://answers.ea.com/t5/Battlefield-4/PC-This-is-how-to-fix-BF4-after-everything-else-failed-to-fully/m-p/2994150#M130751
