Connection problems but can't tell if its my Internet provider or the xbox? Help!

Ok, so I finally got gold membership and xbox live was working perfectly. Then 2 to 3 weeks ago, xbox live just became dumb.

1. Singing takes forever with slight chance of freezing

2. Once I join a online game, my character flips out be jumping to opposite points on map and people would see me totally fine

3. If I leave and do single player exact same thing in #2

4. Go back to dashboard, xbox live is disconnected but I'm still signed in.

5. Reconnect and it happens all over again

So, I looked up the different error codes I got (5 of them), tryed the solution they gave, but none worked.

I checked the error status report and looked for something with same or similar and tryed what worked for them but still didn't.

Now I'm starting to think its the xbox cause nothing is working. I'll give the error status code but if I get the same answers you usually get if u get an error (clear system cashe, disconnect the wires and plug back in) cause I already tryed those, then
tell me if anybody got the same problem and how you fixed it or also have it.

W:0000-0021

X:0400-F001

Y:20A8-4840

Z:0000-0000

ID:FFFF-FFFF

L:8015-100C

Q: 8015-100C

T: Wireless

A: 192.168.1.130/255.255.255.0

G:192.168.1.1

D:68.105.28.11, 68.105.29.11

Modem: SB5120

Router: Cisco Valet

:)

 

Can't download DLCs for Microsoft Flight

When I try to download the DLC that I already bought it tells me "An error occurred with the Games for Windows - LIVE client. If you ignore this issue, you will still be able to play your game but you will be unable to manage or download any Marketplace
content. If you choose to troubleshoot this issue, the game may minimize or your session may end." so when I click troubleshoot it minimizes my game and then tells me "Connection error can't start the program. There may be a problem with your Internet connection
or the LIVE service. Open Internet Explorer and try to open a Web page. If you can't, contact your Internet Service Provider (ISP). If you can browse the Internet, you can find more help in the Internet connection problems help file." so when i click troubleshoot
again it tells me "Troubleshooting couldn't identify the problem"

 

Consistent Disconnection from XBL (this hasnt been solved yet..Ive checked)

same problem here its been like this for a month now.followed all the trouble shooting steps contacted my internet provider no problems with them or my connection, so come on microsoft sort it out.