dakoon2003

While true its not clear you can click "Custom Price" and input $0 dollars.

Try Elementary OS, its based off ubuntu and is almost a dead ringer for OSX. It has the window management you are looking for as well as a couple of apps. Try Synapse as a replacement for Alfred.

Best advice I have is the 20/20 rule.. I used to do the same thing. I changed the lighting in my office. Dim light except for the monitor. I use Flux to adjust the brightness depending on the time of day. And every 20 minutes I try to focus on something at least 20 feet away. It helps keep eyestrain at bay which is what causes most headaches. Also swap tea for coffee, water for cokes, and I use apps like focus to stop distractions.