the volume cutter would be a great choice and has room for big tires, which are key. and yes, clydesdales will have good general information about wheels and tires. i'd go with all city hubs, 36 straight gauge spoke wheels, 35c tires, and deep-v's. chuckers are a little too burly for a bike that won't be tricked.

i would also suggest a good crankset, or at very least a euro bb BMX crankset, since that's where a lot of the weight is transferred through the frame.

if you get the right parts in those areas, you'd probably do just as well on a steamroller or scrambler as you will on the cutter. 300 is a lot of weight but unless you're doing stair gaps the forces on the frame should be minimal. if you hop curbs, get the cutter. if you just ride, a scrambler would be fine.

of course, if anything installed improperly, it will break. same goes for handbuilt wheels.