MacOS – Will Mac Mini i5 OSX 10.7.5 Boot in 64 Bit Mode

I have the same generation MBA. You don't specify 11 or 13 inch, and that makes a potential considerable CPU difference, but on my 11" 1.6Ghz 4Gb RAM Air I have played Civilization V just fine. Slows down a little as the game progresses, but looks good and plays perfectly acceptably to me.

I got the "System is low on disk space/memory" error as well as a number of other intermittent problems when I upgraded my original apple memory. It turned out to be either bad memory, or marginal timing specs.

Startup disk has no more space available for application memory?

When I put the original memory back in, the problems went away - so try that if you've exhausted your other options.

I did eventually do a little more research and found a 16GB set that very closely matched Apple specs for my early 2011 macbook pro 17 memory, and it's had no problems for several months now.

I suggest trying out the original apple memory and seeing if the problem goes away. If it does, return the memory you have, and see if you can get a different set that works better.