Try adjusting your AC Frequency down to 40 Hz. At that amperage you should have no arc stability problems and the low frequency range available in the Dynasty is incorperated specifically for what you are doing. Also you might try lowering your AC Balance down to 70 or 75%. your photo #2 did not show real great etching.
Furthermore, your high amperage welding arc may be disturbing gas coverage, you could do some trials increasing your shielding gas flow in small incriments up to about 35 cfh, Fillits have a tendency to hold cover gas nicely so also check your torch angle and stand-off distance to be sure your form is good. (a poor torch angle will foul up all your good prep and parameters)
Your electrode appears to be in reasonable condition, Thorium is suitable as long as it does not split or grow little balls at the end (If you see this, know that you are transferring tungsten into the weld). Helium is also a great Idea when you are at the ragged edge of your powersource's output range. If you are equipped, a 50/50 mixture will do wonders.
I'm assuming that your welding 6061 Aluminum.. if not all bets are off :)
Let us know how you progress
Lawrence