You'll need a worsted weight yarn for that gauge. Worsted weight yarns aren't all the same, some are thicker than others. You may need to use different size needles to make gauge. Whichever yarn you decide you want to use - I'd suggest buying one skein/ball/hank to play with and make sure you like it before investing in enough for the sweater. You can do some swatches and wash them as you'd expect to wash the sweater, block them, whatever you want to know what you're working with.
Denial, anger, bargaining, depression, acceptance...the five stages of frogging.