1)
What is the significance of a little Shenos and Tenumos?
1.
Malbim: Shenah is a deeper sleep than Tenumah. Tenumah after Shenah is for pleasure; it is not needed. After waking from Shenah, he still dozes - he is half asleep.
2)
Why does it add "Me'at Chibuk Yadayim Lishkav"?
1.
Malbim: Even after he wakes from dozing, he clenches his arms to lie more on his bed, and is too lazy to don his garments.