1. No, can just close to original, at most 2 and half hours for your case. You must looking for a extended battery pack or external one. Now a day, most people use the battery system as UPS(interruptible power supply) only, to prevent lose of working document.
2. You gonna lose your battery warranty, and if it stated in your warranty document, you lose the warranty of the notebook as well since you using third party accessory.
3. RM179 for a 6 cells battery pack. 9 and 12 just don't fit into your pack. If battery hour really mean a lot to you, I suggest you get an external one from foreign country, just google it "external notebook battery" around RM400-600 I think.

Beside, if you are not playing game, try to use the software come with your notebook for power optimizing setting, set the performance to lower, you will get a lot out of it if you simply surf internet and listen to mp3.