Personally I'm more of a Linux fan but I have Windows 10 Technical Preview on a Virtual Machine on my desktop and it is MUCH better than windows 8. Basically it is Wondows 7 with the look of a more modern OS (similar to 8 but not quite 8) and has some functionality improvements such as multiple desktops and the Windows Updater installing drivers instead of other software. I am personally very exited for Windows 10 to be fully released!
You need the 64 bit version of java to be able to allocate more than 1GB of RAM if you do not already have it. You also need to get rid of the "MaxPermSize=128M" option as they got rid of it in java 8.
Yes, you need to put your skin as a 1.6 skin otherwise it will not work. There are different formats for skins in between some versions, meaning that it will look weird when using a 1.8 skin on 1.6 Minecraft.