Possibly your tungsten is sticking out too far. You said it was sticking out 1/2 the diameter of your cup opening. Typically it should stick out no more than 3 times the diameter of your tungsten with normal cups and 3 to 6 times the electrode diameter with a gas lens front end in draft free areas(I am quoting this from CK Worldwide "Technical Specifications for TIG Welding"). There are exceptions to this rule of course.

My HF helmet works great as low as 10 amps. I don't think it is a helmet problem because that would have nothing to do with getting a good arc and good puddle formation stated by the OP.

Thurmond