I know you want to avoid 17 but here is another option:
Take 40 toward Wilmington NC off 95
Just before Wilmington take the Brunswick County Beach ( 17 S ) exit
Take 17S toward MB, 10 miles S of Shallotte NC turn right on Hickman Road ( 1/2 mile past Brunswick Golf Plantation )
Follow Hickman Road to State line, then keep straight on SC rd ( 57 I think ), about 8-10 miles
Turn left @ light about 4 miles into SC then after 1/2 mile get on 31 bypass which will carry you to / around MB
Only 2 lane will be about 8-10 miles ( Hickman Rd / SC57 ). You will be on 4 lane 17 when on it. Also, on Hickman Road just at State line there is a great little farm market, fresh veggies etc. Indigo Farms..I think they have a website.