Downfeed is microadjustable. It's cool as hell, but I wouldn't want to cut many slots with it--I'm betting the quill bearings would not hold up well. Maybe the builder built it for specific projects and had fun doing it.
I'd be interested in that X-Y table. I'd let the seller know that price is way too high for a modified Walker Turner DP. The table might be worth $200-$300 depending on the maker and age.