Throwing it hard is not the ultimate goal here. Repetition is of great importance in bowling, so less muscle used is usually better. Definitely you should go heavier. I'm 50 years old and throw 15 lbs, like most of us on here. If you get properly fitted you should easily handle 14 or 15 lb. equipment.
One ball that would be an easy choice for your next step would be the DV8 Reckless. It's strong, smooth read on many shots would be a versatile pick, too. There will be a multitude of opinions now that you've asked, so good luck as you return to the sport we love.