I'm assuming the bike has rim brakes and 130mm OLD rear hub. 130mm 11-speed hubs have a lot of offset. A truly durable wheel for a 300lb rider is going to require either and offset rim or a fairly deep rim. Rim depth and offset both help to balance out the left/right spoke tension, which reduces fatigue on the spokes, rim, and hub.

Just looking at offset 700c rims with a braking surface, the list is pretty short: Velocity A23, Kinlin XR31, Kinlin XR22, Kinlin XR26, Pacenti Forza. Those are all available in 32H, and half are available in 36H. You could also consider the non-offset DT Swiss R511, but not for a first build (nipple washer and proprietary nipples). For my money, I'd go with the Kinlin XR31 offset rim, either 32 or 36H.

White Industries T11 would probably be the best option (high flange, Ti freehub, steel axle all help with durability). For bonus points, it's available in 32 and 36H in red.

That leaves spokes. You can't go wrong with Sapim Force, Sapim CX Sprint, or DT Swiss Alpine III.

FWIW, I've been building and using a fair number or 32H rims and hubs on tandem wheels (in addition to 36H and 40H). The weights are pretty similar to the OP. The big difference with the tandem wheels is that the hubs are 148mm thru axle or 145mm QR, so the non-drive-side spokes can carry a fair bit of load.