I will echo the 'be careful' warnings. But the decision is yours! A 12' zodiac with a 20hp is not a typical fishing boat but it is definitely a very buoyant and quick little craft. It will handle definitely handle a typical day of erie weather just fine with a skilled operater. The biggest worry is having a trustworthy, reliable motor. Offshore is not a place to be dealing with any potential problems. A GPS, weather app on a phone and 100% reliable communication is a must.
Not sure what area your referring to as Longpoint Shoal? Nanticoke shoal isnt too bad of a run for a smaller boat later on in the year. Jigging can work but may not be the most productive option. A couple dipsey divers or even long lining crank baits with or without an extra weight/diver will put fish in the boat more consistently. The Walleye fishing in that area tends to heat up a little later as it warms rather slowly.
Josh