Yes, you need more sealant and need to get the tire fixed. The air compressor is good, nothing to replace on that.
BE SURE to tell the person fixing your tire that you used fix-a-flat. Some places will check the tire and think nothing is wrong since the mobility kit temporarily stopped the leak.
The mobility kit is the same thing as a can of fix-a-flat. Except the can is cheaper and easier to use.
2013 F30 328i Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red