If you're looking for a meeting place or a good stop around ½ or halfway between Sinamar and Domalandan, you can try Joson, Philippines, which is about 4 hours southwest of Sinamar, or about 3½ hours east of Domalandan.
About ¼ or a fourth of the way, you can stop at Solano, Philippines. This is about 1½ hours southwest of Sinamar.
About ⅓ or a third of the way, you can stop at Bambang, Philippines. This is about 2½ hours southwest of Sinamar.
About ⅔ or two thirds of the way, you can stop at Lupao, Philippines. This is almost 5 hours southwest of Sinamar, or about 2½ hours east of Domalandan.
About ¾ or three fourths of the way, you can stop at Carosucan, Philippines. This is about 5½ hours southwest of Sinamar, or almost 2 hours east of Domalandan.
If you drive straight through without stopping at all, the total distance is 304 km. 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 7 hours, 18 minutes.