Regarding the hull type, the dealer was right - the Hewescraft 160 is fine in calm waters, but there are occasional waves in Puget Sound, and the flat-bottomed models (such as the Sportsman) are indeed prone to jolting. The Pro-V 18 will have much better stability. The V-shaped bottom cuts the waves more smoothly. Moreover, the 18-foot size takes into account both towing and space, and it is just right for your jeep's 3,500-pound towing capacity.
If you occasionally want to bring guests along, you can actually look at aluminum boats like Alumaweld Stryker 17 or Northwest 1800 Commander. There are many local brands on the West Coast, and they are also available in the second-hand market. If you want to store ships in winter, many docks in the Pacific Northwest have indoor storage facilities, and the monthly rent is not expensive either
In fact, if you can find a well-maintained second-hand Pro-V, it offers great value for money! After all, you and your spouse use it most of the time, so there's no need to buy a new boat. Take a test drive first and then decide.