DC TIG is very similar to O/A welding. Instead of a flame, you have an arc that acts like an adjustable flame (sort of ). If you get too close with the flame, it will pop--same with the W. If you hold the flame in one area too long, it will melt through. My suggestion would be to get to know the machine without the pulse first. You learn to do the pulsing with your foot. "Accelerate" on the pedal, get a puddle going, back off if you need to, add a little filler to the puddle, decel but don't extinguish, move the torch, repeat. Pay attention to the color of the hot steel and the "wetness" and back off the pedal if necessary to keep it from drooping out on you. Adding filler can cool the weld, also. Turn the piece over when done and look at your HAZ--it should be a uniform distance away from the weld. If it got wider as you went along you were putting too much heat into the work and will need to adjust your speed and/or heat. It is hard for me to evaluate your work because it appears you took it to the wire wheel. PS: learn to get good with steel before you move to aluminium. Al doesn't change color with heat like Fe does and you need to be more aware of the "wetting" or the point where metal changes state from a solid to a liquid... PPS: when welding over a void like the pinhole pic, make sure the Ar is turned up a little to help push the atmosphere out of the void. 25cfm is a good start.