Would advise you getting copies of all your lab results and filing them in a folder or whatever way suits you. You may not understand what the levels mean now but in time you will start to make sense of them. If you care to post your ACTH results here we may be able to make suggestions.
Dex 0.5mg is not a very low dose for LOCAH - (contrary to what your endo said), but it was a good dose to start you on to get your levels under control initially. Probably a good move to try you on 0.25mg and see what happens.
You've always got the option of taking 0.375mg of Dex if 0.25mg proves to be not enough. You've furthermore got the option of trying one of the 'gentler' steroids like Hydrocortisone or Prednisolone/Prednisone.
Regarding the 8 week period - I remember those! I was never on Dex but on Pred during the years when that happened to me. Never really got a solution for it but I probably didn't pursue a solution, just put up with it - but that was a long time ago and I have Classic CAH not LOCAH! So I'm next to useless for any advice on that one!!