iPhone 4 Sleep/wake button, vibrate button, and volume button not responsive

My iPhone's been through hell.
1. Friend threw my iPhone against the wall cause he was pissed, broke the led screen, replaced it myself, then messed up all the screws. Only one doesn't fit though, used a tiny piece of electrical tape, and it works.
2. 2weeks after, I accidentally dropped my iPhone on the carpet, and for some odd reasons after, my sleep/wake button, the volume + and - buttons , the silent on/off button are unresponsive. On top of that, my sensor top left of the facetime camera is also not working. Whenever i talk on the phone the screen stays on, and I might accidentally press the speaker with my face. I mean iPhone 5 comes out soon, but I still want to fix it.

Point is, does anyone know what is the problem? I don't know if its the flex cables (but the side buttons and the sleep/wake button + the sensor are on different flex cables, so a coincidence both of them are malfunction?) or my logic board?

edit: Buttons do click, they are not stuck. However my sleep wake button was stuck a month ago, and I slipped a tiny piece of plastic plate between, and it works perfectly. I don't think that affect this situation anyway.

edit 1: I opened it up, and found out that the flex cable is loose for the sleep wake button, (because I disassemble countless times) however upon impact when the sleep/wake button fell off, it ripped the volume flex cable apart. The cable were separated in half. Just bought a new one online from eBay.
Thank you for helping

 

No, because I brought this when it first came out, and it the iPhone 4, so the warranty is up, years back. They would just simply to buy me a new one. I brought my 3gs back once, and they told me that they don't know what's wrong, they would have to open it up and thats going to cone money. Sometimes, they wont even fix it.

 

no, my girlfriend took the upgrade, she got an iPhone too