Last night I decided to get rid of Windows from my laptop as I almost never use it anymore and it wastes valuable space (I think this is a Windows killing feature

).
So I backup my data and wiped my disk so I can perform a clean install. I'm using a liveUSB of TR 2012.06 full and Disk Drake for partitioning.
My plan was to create the following partitions:
1. /root
2. /swap
3. /home
and leave about 50gigs free for future use.
Question no1:Should I create separate /boot and /usr partitions? Is there a huge benefit by doing this?
Question no2:My laptop has 4GB of DDR3 memory. Is a swap partition really necessary? I have used a 4GB swap partition in all my installs so far and it is rarely used by the O/S.
Question no3:Creating the first partition for /root takes the number /dev/sda1 (primary)
Creating the second partition for /swap takes the number /dev/sda5 (extended)
Creating the third partition for /home takes the number /dev/sda6 (extended)
Shouldn't that be sda2? I tried to set the second and third partitions as primary through Disk Drake's advanced settings but I still get the same numbering.
Of course it isn't something that causes trouble or very important, I was just wondering why is this happening.