After only 3-4 weeks in the fermenter, I doubt you'll need to re-pitch, but it is cheap insurance.
If you do, just use 1-2 g of dry yeast, and definitely rehydrate. Going into a ~12% ABV beer is going to be tough on the yeast either way, and rehydrating will maximize the viability. I'd used something more flocculent than US-05, like Nottingham or S-04.