I'm no expert but I paint quite a bit, so here's my 2 p's worth.
The fact you have to pull the trigger all the way back to get paint out suggests no.1 that the paint is too thick (confirmed by the fact you say you haven't thinned it), and no.2 you've probably got a paint build up inside the nozzle, which gets worse on non thinned paint.
Also, you should be able to spray at around 10 psi for detail work, but the paint needs to be thinned even more for that to work, and that's why you're getting the paint spattering out, as its not atomising because you need more pressure due to the thicker paint.
The spidering you are getting is likely due to you trying to use too high of a pressure. Try thinning the paint and reducing air pressure