If you're looking for a meeting place or a good stop around ½ or halfway between Pataskala and Gallipolis, you can try Athens, OH, which is about 1 hour southeast of Pataskala, or almost an hour north of Gallipolis.
About ⅓ or a third of the way, you can stop at Pine Grove, OH. This is about half an hour south of Pataskala.
About ⅔ or two thirds of the way, you can stop at Pratts Fork, OH. This is about 1½ hours southeast of Pataskala, or about half an hour north of Gallipolis.
About ¾ or three fourths of the way, you can stop at Darwin, OH. This is about 1½ hours southeast of Pataskala, or about half an hour northeast of Gallipolis.
If you drive straight through without stopping at all, the total distance is 110 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 2 hours, 2 minutes.