Here's an update, as I've recently had an opportunity to drive through the area:
There
is a good path along the ~2km stretch of the A495 between the ODP and the village of Llynclys. There is no significant elevation change along the way, so the additional distance shouldn't add a great degree of difficulty.
The
Bridge House looks like a nice place to stay. (We only saw it from the outside, but their website also gives helpful information). The White Lion Pub is very close (~100 meters). There's also another pub called
The Lime Kiln about 0.5 mi east of the ODP on the A495. It appears to be a somewhat upscale pub -- booking may be necessary at times -- but their food has received excellent reviews.
We'll probably try to stay here during our walk, so we'll report back here afterwards. Perhaps we'll have further information on the Archaeolgical Study Centre as well.