1. Yes it will work with a Mac as it just plugs into a USB slot and you turn off the WiFi adapter in your puter.
2 & 3. Not enough signal loose to worry about through glass so with a long enough USB cable you should be able to point through a side window. Have never tried it through a side as have plenty of windows. If the side is alum then it's going to knock the signal down. Sometimes I do not have to use the Yagi antenna as the signal is strong enough for the little stub antenna to work.
4. Yes you can pay $40+ plus for the same thing (300MB) that's $14 from China where they are all made.
5.A yagi antenna is a yagi antenna so I doubt there is a 10db difference in the two. In the first link it included a USB adapter but at only 150MB speed. I did not find a cheap combo with a 300MB adapter so I suggested buying each item to get the higher speed. $19 for 150MB or $26 for 300MB and MAYBE a better antenna... your choice although many hot spots are s l o w.
