We took your route in reverse today, going from Hwy 7 about ten miles south of Henderson and offer the following notes from your direction.
From Springdale to probably about 10 miles west of Osage, AR 412 is a nice four lane highway. Then it turns into a two lane highway, with passing lanes every so often. This two lane highway is very scenic and pretty, but is slow driving. It is twisty, turny, curvy and up and down hill. It's not bad though; we enjoyed the drive but were not in any hurry. There are no switch-backs, just normal curves. You should have no problems on 412.
I'm not sure how you are going to get to Hwy 43 that goes to Ponca, but we went Hwy 392 south off Hwy 412 before getting to Harrison, then south on Hwy 397 to Hwy 43. 392 and 397 are small state or county roads, but are doable.
Do you have a planned route to get to Ponca after leaving 412? You may can call the BOC and ask them for directions once you get off 412.
Wade & Debby Griffin
2018 Tiffin Allegro Open Road 32SA, 24K/30K Ford F53
2012 Jeep Liberty