I completely understand your frustration....I too have an Aztek, model 4709 (I think), and as you'll notice from my posts below, mine broke and I've since purchased an Iwata.
Now, I am pretty new to this, but I too had problems I sought answers on specifically related to the same issue, my camo on German armor was in my opinion, too thick. What I was told was to turn the pressure down, and hold the airbrush extremely close to the model. When I did this, I was able to get a finer line (still not what I for sure wanted, but much better) and since the pressure was so low, I didn't have any of the spidering with the paint. Also, I was using Tamiya acrylics....I've never airburshed enamels, so perhaps my suggestion won't work. As in your picture, for any fine lines I used the tan nozzle, and always broke it down into its three pieces and thoroughly cleaned it.
If you are thinking about a new airbrush, if you're looking at an Iwata, everyone recommends Dixieart.com. I purchased the Eclipse from my local Hobby Lobby and with using the 40% off one item coupon printed from the internet (twice), I was able to purchase the Eclipse and hose for $90 ($78 for the airbrush and $12 for the hose). This was about $40 cheaper than Dixieart. Also, if you're interested in Badger, I believe that is the brand Michael's craft stores carry and if you get their 40% off newspaper coupon, you could probably get something cheaper than the Iwata, I think my store had the Anthem and Crescendo.
Again, info from a newbie, so take it for what it is worth...
Randy