5.) It is possible. Depending on your motherboard you may be able to upgrade the processor. Also If the video is not onboard, it may also be swapped. More info needed (Manufacturer, motherboard model number, video card onboard?)
8.)Short answer no. Long answer, If the video card is onboard dedicating more memory isn’t going to help. The video is using a portion of your processor, and its just a very inefficient system for max fps.
It is possible that you can increase your fsb, maybe. But even that will provide <%5 gains in your fps.
Its been said a few times, that machine was never meant to run modern graphics intense games. It’s that old polishing a turd adage.