Flame on Stove is very high and out of control...

Part of your answer to the change in flame and build-up is the change from softwood to hardwood pellets. From my limited experience and what I`ve learned here, hardwood pellets would need more air to burn efficiently.

The overtemp has never tripped... I have been running it on day 3 on setting 3 and haven't changed it at all. It'll be interesting to see what the burn pot looks like tonight. I suppose my concern is more the burn pot clogging with ash. This only started this year and my understanding is the ash will effect the air flow which will effect the stove. If it only happens on the higher setting though I can live with that, I normally never run it over 3.

I've tried more air and it seems to control the flame better (although it is still very high) but I still get the hard ash build up in the burn pot.

I think it's normal to see clinkers when running on high. There's more fuel, and the air sometimes isn't enough to burn completely. I got them after a day or so on higher settings as well, but on 3, i can run for a week or 2 without cleaning the pot, including for restarts.