1. It is not a question of whether or not this processor can support Android or Linux (it certainly can), it is a question of whether or not the BIOS will support booting from any source other than the Windows eMMC (and specifically from a USB device). If it does, you should be able to boot from, for example, a Linux installation image. To be honest and forthcoming, I am thinking that, if you have to ask this question, you may not have the skills to pull this off.
2. As you've surmised, you cannot replace the processor in these tablets. It is unlikely that they are pin-compatible and, if they were, they are soldered-down BGA devices and it is unlikely that the Atom could be removed without damaging the board (let alone the Core i5 be soldered down by hand successfully). As the same time, it is unlikely that the firmware (BIOS) on the board will have support for processors other than the Atom (to truly answer this question, you would need to talk to Samsung's technical support folks). For similar reasons, it is also unlikely that you can increase the DRAM allotment. They are also typically soldered-down devices and difficult to replace.
Hope this answers it,